Update ubuntu-18.04 to 20.04

.github/workflows/rust.yml

@@ -21,7 +21,7 @@ jobs:
     strategy:
       fail-fast: false
       matrix:
-        os: [ubuntu-18.04, macos-latest, windows-latest]
+        os: [ubuntu-20.04, macos-latest, windows-latest]
     steps:
     - uses: actions/checkout@v3
     - name: Cache dependencies
@@ -40,7 +40,7 @@ jobs:
   # We run tests in debug also, to make sure that the debug_assertions are hit
   test-debug:
     name: Run tests in debug
-    runs-on: ubuntu-18.04
+    runs-on: ubuntu-20.04
     steps:
       - uses: actions/checkout@v3
       - uses: actions-rs/toolchain@v1
@@ -58,7 +58,7 @@ jobs:
 
   clippy:
     name: Run Clippy
-    runs-on: ubuntu-18.04
+    runs-on: ubuntu-20.04
     steps:
       - uses: actions/checkout@v3
       - uses: actions-rs/toolchain@v1
@@ -77,7 +77,7 @@ jobs:
 
   fmt:
     name: Run Rustfmt
-    runs-on: ubuntu-18.04
+    runs-on: ubuntu-20.04
     steps:
       - uses: actions/checkout@v3
       - uses: actions-rs/toolchain@v1