github: update cache version from deprecated v1 to v4

Author: bhandras

.github/workflows/main.yml

@@ -75,7 +75,7 @@ jobs:
           fetch-depth: 0
 
       - name: go cache
-        uses: actions/cache@v1
+        uses: actions/cache@v4
         with:
           path: /home/runner/work/go
           key: lnd-${{ runner.os }}-go-${{ env.GO_VERSION }}-${{ github.job }}-${{ hashFiles('**/go.sum') }}
@@ -107,7 +107,7 @@ jobs:
         uses: actions/checkout@v2
 
       - name: go cache
-        uses: actions/cache@v1
+        uses: actions/cache@v4
         with:
           path: /home/runner/work/go
           key: lnd-${{ runner.os }}-go-${{ env.GO_VERSION }}-${{ github.job }}-${{ hashFiles('**/go.sum') }}