remove macOS runner (#396)

.github/workflows/coverage.yml

@@ -13,13 +13,6 @@ on:
       - "evm-template/**"
       - "**.md"
       - "**.adoc"
-  workflow_dispatch:
-    inputs:
-      test-macos:
-        description: "run tests on macOS"
-        required: true
-        default: false
-        type: boolean
 
 # If new code is pushed to a PR branch, then cancel in progress workflows for
 # that PR. Ensures that we don't waste CI time, and returns results quicker.
@@ -42,19 +35,7 @@ env:
 
 jobs:
   clippy-fmt-test:
-    strategy:
-      fail-fast: false
-      matrix:
-        os:
-          - ubuntu-22.04
-          - macos-12
-        run-all:
-          - ${{ inputs.test-macos == true || github.ref == 'refs/heads/main' }}
-        exclude: # exclude macos-12 when the condition is false
-          - run-all: false
-            os: macos-12
-
-    runs-on: ${{ matrix.os }}
+    runs-on: ubuntu-22.04
     defaults:
       run:
         working-directory: ./
@@ -74,7 +55,7 @@ jobs:
         uses: actions-rust-lang/setup-rust-toolchain@v1
         with:
           components: clippy, rustfmt
-      
+
       - name: "Install cargo-llvm-cov"
         uses: taiki-e/install-action@v2
         with: