GH Actions: version update for various predefined actions

A number of predefined actions have had major release, which warrant an update to the workflow(s).

These updates don't actually contain any changed functionality, they are mostly just a change of the Node version used by the action itself (from Node 14 to Node 16).

Refs:
* https://github.com/actions/checkout/releases

P.S.: looks like there are some more actions in use which have had new major releases. As those actually _do_ contain changed functionality, I've excluded the others from this PR.

.github/workflows/continuous-integration.yml

@@ -64,7 +64,7 @@ jobs:
 
     steps:
       - name: "Checkout"
-        uses: "actions/checkout@v2"
+        uses: "actions/checkout@v3"
 
       - name: "Install PHP"
         uses: "shivammathur/setup-php@v2"
@@ -138,7 +138,7 @@ jobs:
 
     steps:
       - name: "Checkout"
-        uses: "actions/checkout@v2"
+        uses: "actions/checkout@v3"
 
       - name: "Install PHP"
         uses: "shivammathur/setup-php@v2"

.github/workflows/lint.yml

@@ -22,7 +22,7 @@ jobs:
 
     steps:
       - name: "Checkout"
-        uses: "actions/checkout@v2"
+        uses: "actions/checkout@v3"
 
       - name: "Install PHP"
         uses: "shivammathur/setup-php@v2"

.github/workflows/phpstan.yml

@@ -25,7 +25,7 @@ jobs:
 
     steps:
       - name: "Checkout"
-        uses: "actions/checkout@v2"
+        uses: "actions/checkout@v3"
 
       - name: "Install PHP"
         uses: "shivammathur/setup-php@v2"

.github/workflows/release.yml

@@ -14,7 +14,7 @@ jobs:
     runs-on: ubuntu-latest
     steps:
       - name: Checkout code
-        uses: actions/checkout@v2
+        uses: actions/checkout@v3
 
       - name: "Install PHP"
         uses: "shivammathur/setup-php@v2"