[ops] github workflow update macos-12 (#4248)

Co-authored-by: Nita Neou (Soph) <soph@harmony.one>

.github/workflows/ci.yaml

@@ -40,7 +40,7 @@ jobs:
     if: needs.check.outputs.tag_annotated == 'true'
     strategy:
       matrix:
-        os: [ubuntu-18.04, macos-10.15, [self-hosted, linux, ARM64]]
+        os: [ubuntu-18.04, macos-12, [self-hosted, linux, ARM64]]
 
     steps:
       - name: Import GPG key
@@ -102,7 +102,7 @@ jobs:
         working-directory: harmony
 
       - name: Build harmony binary and packages for MacOS
-        if: matrix.os == 'macos-10.15'
+        if: matrix.os == 'macos-12'
         run: |
           brew install bash
           sudo rm -f /usr/local/opt/openssl