ci: run actions on ubuntu 20.04

.github/workflows/lint.yml

@@ -5,7 +5,7 @@ on: [push, pull_request]
 jobs:
   luacheck:
     name: Luacheck
-    runs-on: ubuntu-latest
+    runs-on: ubuntu-20.04
     steps:
       - uses: actions/checkout@v1
 
@@ -21,12 +21,11 @@ jobs:
 
   stylua:
     name: StyLua
-    runs-on: ubuntu-latest
+    runs-on: ubuntu-20.04
     steps:
-    - uses: actions/checkout@v2
-    - name: Stylua
-      uses: JohnnyMorganz/stylua-action@1.0.0
-      with:
-        token: ${{ secrets.GITHUB_TOKEN }}
-        args: --check .
-
+      - uses: actions/checkout@v2
+      - name: Stylua
+        uses: JohnnyMorganz/stylua-action@1.0.0
+        with:
+          token: ${{ secrets.GITHUB_TOKEN }}
+          args: --check .

.github/workflows/tests.yml

@@ -9,7 +9,7 @@ jobs:
         nvim_tag: [v0.5.0, v0.5.1, v0.6.0, v0.6.1]
 
     name: Run tests
-    runs-on: ubuntu-latest
+    runs-on: ubuntu-20.04
     env:
       NVIM_TAG: ${{ matrix.nvim_tag }}
     steps:

.github/workflows/update-readme.yml

@@ -5,7 +5,7 @@ on: push
 jobs:
   update-readme:
     name: Update README
-    runs-on: ubuntu-latest
+    runs-on: ubuntu-20.04
     steps:
       - uses: actions/checkout@v1