Changed CI to just run on ubuntu-latest

If we already have to bump this version as GitHub phases out older
Ubuntu runners (which is reasonable), I don't really see the value of
pinning a specific version. We might as well just respond to any
broken dependencies caused by GitHub's implicit updates as they
happen...

It's not like CI is truly continuous.

.github/workflows/post-release.yml

@@ -10,7 +10,7 @@ defaults:
 
 jobs:
   post-release:
-    runs-on: ubuntu-22.04
+    runs-on: ubuntu-latest
     steps:
       # trigger post-release in dependency repo, this indirection allows the
       # dependency repo to be updated often without affecting this repo. At

.github/workflows/release.yml

@@ -11,7 +11,7 @@ defaults:
 
 jobs:
   release:
-    runs-on: ubuntu-22.04
+    runs-on: ubuntu-latest
 
     # need to manually check for a couple things
     # - tests passed?

.github/workflows/status.yml

@@ -11,7 +11,7 @@ defaults:
 jobs:
   # forward custom statuses
   status:
-    runs-on: ubuntu-22.04
+    runs-on: ubuntu-latest
     steps:
       - uses: dawidd6/action-download-artifact@v2
         continue-on-error: true
@@ -60,7 +60,7 @@ jobs:
 
   # forward custom pr-comments
   comment:
-    runs-on: ubuntu-22.04
+    runs-on: ubuntu-latest
 
     # only run on success (we don't want garbage comments!)
     if: ${{github.event.workflow_run.conclusion == 'success'}}

.github/workflows/test.yml

@@ -14,7 +14,7 @@ env:
 jobs:
   # run tests
   test:
-    runs-on: ubuntu-22.04
+    runs-on: ubuntu-latest
     strategy:
       fail-fast: false
       matrix:
@@ -329,7 +329,7 @@ jobs:
   #
   # this grows exponentially, so it doesn't turn out to be that many
   test-pls:
-    runs-on: ubuntu-22.04
+    runs-on: ubuntu-latest
     strategy:
       fail-fast: false
       matrix:
@@ -359,7 +359,7 @@ jobs:
 
   # run with LFS_NO_INTRINSICS to make sure that works
   test-no-intrinsics:
-    runs-on: ubuntu-22.04
+    runs-on: ubuntu-latest
     steps:
       - uses: actions/checkout@v2
       - name: install
@@ -376,7 +376,7 @@ jobs:
 
   # run LFS_MULTIVERSION tests
   test-multiversion:
-    runs-on: ubuntu-22.04
+    runs-on: ubuntu-latest
     steps:
       - uses: actions/checkout@v2
       - name: install
@@ -393,7 +393,7 @@ jobs:
 
   # run tests on the older version lfs2.0
   test-lfs2_0:
-    runs-on: ubuntu-22.04
+    runs-on: ubuntu-latest
     steps:
       - uses: actions/checkout@v2
       - name: install
@@ -412,7 +412,7 @@ jobs:
 
   # run under Valgrind to check for memory errors
   test-valgrind:
-    runs-on: ubuntu-22.04
+    runs-on: ubuntu-latest
     steps:
       - uses: actions/checkout@v2
       - name: install
@@ -434,7 +434,7 @@ jobs:
   # test that compilation is warning free under clang
   # run with Clang, mostly to check for Clang-specific warnings
   test-clang:
-    runs-on: ubuntu-22.04
+    runs-on: ubuntu-latest
     steps:
       - uses: actions/checkout@v2
       - name: install
@@ -457,7 +457,7 @@ jobs:
   #
   # note there's no real benefit to running these on multiple archs
   bench:
-    runs-on: ubuntu-22.04
+    runs-on: ubuntu-latest
     steps:
       - uses: actions/checkout@v2
       - name: install
@@ -533,7 +533,7 @@ jobs:
 
   # run compatibility tests using the current master as the previous version
   test-compat:
-    runs-on: ubuntu-22.04
+    runs-on: ubuntu-latest
     steps:
       - uses: actions/checkout@v2
         if: ${{github.event_name == 'pull_request'}}
@@ -569,7 +569,7 @@ jobs:
 
   # self-host with littlefs-fuse for a fuzz-like test
   fuse:
-    runs-on: ubuntu-22.04
+    runs-on: ubuntu-latest
     if: ${{!endsWith(github.ref, '-prefix')}}
     steps:
       - uses: actions/checkout@v2
@@ -619,7 +619,7 @@ jobs:
 
   # test migration using littlefs-fuse
   migrate:
-    runs-on: ubuntu-22.04
+    runs-on: ubuntu-latest
     if: ${{!endsWith(github.ref, '-prefix')}}
     steps:
       - uses: actions/checkout@v2
@@ -691,7 +691,7 @@ jobs:
 
   # status related tasks that run after tests
   status:
-    runs-on: ubuntu-22.04
+    runs-on: ubuntu-latest
     needs: [test, bench]
     steps:
       - uses: actions/checkout@v2