chore(ci): use major cache action version (#408)

Author: caarlos0

.github/workflows/build.yml

@@ -33,7 +33,7 @@ jobs:
           repo-token: ${{ secrets.GITHUB_TOKEN }}
       -
         name: Cache Go modules
-        uses: actions/cache@v2.1.6
+        uses: actions/cache@v2
         with:
           path: |
             ~/go/pkg/mod
@@ -85,7 +85,7 @@ jobs:
           repo-token: ${{ secrets.GITHUB_TOKEN }}
       -
         name: Cache Go modules
-        uses: actions/cache@v2.1.6
+        uses: actions/cache@v2
         with:
           path: |
             ~/go/pkg/mod
@@ -132,7 +132,7 @@ jobs:
           repo-token: ${{ secrets.GITHUB_TOKEN }}
       -
         name: Cache Go modules
-        uses: actions/cache@v2.1.6
+        uses: actions/cache@v2
         with:
           path: |
             ~/go/pkg/mod