ci/gha: use v3 tag for actions/cache

This tag points to the latest v3 version (currently v3.0.11). Mainly
done to avoid cluttering git history with multiple minor v3 upgrades.

Signed-off-by: Kir Kolyshkin <kolyshkin@gmail.com>

.github/workflows/validate.yml

@@ -72,7 +72,7 @@ jobs:
         echo "VERSION=3.3.1" >> $GITHUB_ENV
         echo "$(go env GOPATH)/bin" >> $GITHUB_PATH
     - name: cache go mod and $GOCACHE
-      uses: actions/cache@v3.0.11
+      uses: actions/cache@v3
       with:
         path: |
           ~/go/pkg/mod
@@ -119,7 +119,7 @@ jobs:
       with:
         go-version: "${{ env.GO_VERSION }}"
     - name: cache go mod and $GOCACHE
-      uses: actions/cache@v3.0.11
+      uses: actions/cache@v3
       with:
         path: |
           ~/go/pkg/mod