ICU-22193 Use Ubuntu 20.04 for jobs failing in migration to 22.04

diff --git a/.github/workflows/icu_ci.yml b/.github/workflows/icu_ci.yml
index 1293e5edbb0cf4e36a90a471c62ff777cc4a8e9a..3c6364be355154306a1e2921e7012dab165c623e 100644 (file)
--- a/.github/workflows/icu_ci.yml
+++ b/.github/workflows/icu_ci.yml
@@ -172,7 +172,7 @@ jobs:
   # (FORCE guards make this tool pass but won't compile to working code.
   # See the testtagsguards.sh script for details.)
   clang-release-build-and-test:
-    runs-on: ubuntu-latest
+    runs-on: ubuntu-20.04
     steps:
       - uses: actions/checkout@v2
 
@@ -261,7 +261,7 @@ jobs:
 
   # Run ICU4C tests with stubdata.
   run-with-stubdata:
-    runs-on: ubuntu-latest
+    runs-on: ubuntu-20.04
     steps:
       - uses: actions/checkout@v2
 
@@ -402,7 +402,7 @@ jobs:
 
   # Build Unicode update tools
   unicode-update-tools:
-    runs-on: ubuntu-latest
+    runs-on: ubuntu-20.04
     steps:
     - uses: actions/checkout@v2
     - uses: bazelbuild/setup-bazelisk@v1