Update actions/checkout action to v2.7.0 (#228)

Co-authored-by: renovate[bot] <29139614+renovate[bot]@users.noreply.github.com>

Author: renovate[bot]

.github/workflows/checks.yaml

@@ -11,7 +11,7 @@ jobs:
     runs-on: ubuntu-latest
     steps:
       - name: check out code
-        uses: actions/checkout@ee0669bd1cc54295c223e0bb666b733df41de1c5 # v2
+        uses: actions/checkout@ee0669bd1cc54295c223e0bb666b733df41de1c5 # v2.7.0
 
       - name: install dependencies
         run: npm install
@@ -23,7 +23,7 @@ jobs:
     runs-on: ubuntu-latest
     steps:
       - name: check out code
-        uses: actions/checkout@ee0669bd1cc54295c223e0bb666b733df41de1c5 # v2
+        uses: actions/checkout@ee0669bd1cc54295c223e0bb666b733df41de1c5 # v2.7.0
 
       - name: install dependencies
         run: npm install
@@ -35,7 +35,7 @@ jobs:
     runs-on: ubuntu-latest
     steps:
     - name: check out code
-      uses: actions/checkout@ee0669bd1cc54295c223e0bb666b733df41de1c5 # v2
+      uses: actions/checkout@ee0669bd1cc54295c223e0bb666b733df41de1c5 # v2.7.0
 
     - name: install dependencies
       run: npm install
@@ -49,6 +49,6 @@ jobs:
   gen-proto:
     runs-on: ubuntu-latest
     steps:
-      - uses: actions/checkout@ee0669bd1cc54295c223e0bb666b733df41de1c5 # v2
+      - uses: actions/checkout@ee0669bd1cc54295c223e0bb666b733df41de1c5 # v2.7.0
       - run: make docker-pull
       - run: make gen-proto