fix ubuntu version to 20.04

Author: Sinestro38

.github/workflows/ci.yaml

@@ -5,7 +5,7 @@ on: [pull_request]
 jobs:
   lint:
     name: Lint check
-    runs-on: ubuntu-latest
+    runs-on: ubuntu-20.04
     steps:
       - uses: actions/checkout@v1
       - uses: actions/setup-python@v1
@@ -19,24 +19,22 @@ jobs:
 
   format:
     name: Formatting check
-    runs-on: ubuntu-latest
+    runs-on: ubuntu-20.04
 
     steps:
       - uses: actions/checkout@v1
       - uses: actions/setup-python@v1
         with:
           python-version: '3.8'
           architecture: 'x64'
-      - name: get ubuntu version
-        run: lsb_release -a
       - name: Install Format tools
         run: pip install --upgrade pip setuptools; pip install -r requirements.txt; sudo apt-get install -y clang-format-6.0
       - name: Format Check
         run: ./scripts/format_check.sh
 
   wheel-build:
     name: Wheel test
-    runs-on: ubuntu-latest
+    runs-on: ubuntu-20.04
 
     steps:
       - uses: actions/checkout@v1
@@ -55,7 +53,7 @@ jobs:
 
   bazel-tests:
     name: Library tests
-    runs-on: ubuntu-latest
+    runs-on: ubuntu-20.04
     needs: [lint, format]
 
     steps:
@@ -73,7 +71,7 @@ jobs:
 
   leak-tests:
     name: Memory Leak tests
-    runs-on: ubuntu-latest
+    runs-on: ubuntu-20.04
     needs: [lint, format]
 
     steps:
@@ -91,7 +89,7 @@ jobs:
 
   tutorials-test:
     name: Tutorial tests
-    runs-on: ubuntu-latest
+    runs-on: ubuntu-20.04
     needs: [lint, format, wheel-build]
 
     steps:

.github/workflows/cirq_compatibility.yaml

@@ -8,7 +8,7 @@ on:
 jobs:
   consistency:
     name: Nightly Compatibility
-    runs-on: ubuntu-latest
+    runs-on: ubuntu-20.04
     steps:
       - uses: actions/checkout@v1
       - uses: actions/setup-python@v1