feat(CI): upgrade to Ubuntu 20.04 (#3106)

.github/workflows/core_build.yml

@@ -13,7 +13,7 @@ jobs:
       matrix:
         compiler: [clang6, clang7]
         modules: [with, without]
-    runs-on: ubuntu-18.04
+    runs-on: ubuntu-20.04
     name: ${{ matrix.compiler }}-${{ matrix.modules }}-modules
     env:
       COMPILER: ${{ matrix.compiler }}

.github/workflows/import_pending_sql.yml

@@ -8,7 +8,7 @@ jobs:
   import-pending-sql:
     strategy:
       fail-fast: false
-    runs-on: ubuntu-18.04
+    runs-on: ubuntu-20.04
     steps:
       - uses: actions/checkout@v2
         with: