SHA pin first-party GitHub Actions

Pins every actions/* and github/* uses: reference in
.github/workflows to its commit SHA within its current major
version, preserving the human-readable version in a trailing
comment. Improves supply-chain posture against tag-mutation
attacks on first-party namespaces.

Follows cli/cli#13491 (cli/cli) and
cli/cli#13490.

Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>

Author: williammartin

.github/workflows/go.yml

@@ -15,12 +15,12 @@ jobs:
     steps:
 
     - name: Set up Go
-      uses: actions/setup-go@v2
+      uses: actions/setup-go@bfdd3570ce990073878bf10f6b2d79082de49492 # v2.2.0
       with:
         go-version: ^${{matrix.go}}
 
     - name: Check out code into the Go module directory
-      uses: actions/checkout@v2
+      uses: actions/checkout@ee0669bd1cc54295c223e0bb666b733df41de1c5 # v2.7.0
 
     - name: Get dependencies
       run: go get -v -t -d ./...