Pin workflows

Signed-off-by: Alex Ellis (OpenFaaS Ltd) <alexellis2@gmail.com>

Author: alexellis

.github/workflows/build.yaml

@@ -12,7 +12,7 @@ jobs:
   build:
     runs-on: ubuntu-latest
     steps:
-      - uses: actions/checkout@master
+      - uses: actions/checkout@v4
         with:
           fetch-depth: 1
       - name: Install Go

.github/workflows/publish.yaml

@@ -20,7 +20,7 @@ jobs:
     runs-on: ubuntu-latest
 
     steps:
-      - uses: actions/checkout@master
+      - uses: actions/checkout@v4
         with:
           fetch-depth: 1
       - name: Install Go