docs(readme): fix accidentally set to checkout@v3

Author: bradennapier

README.md

@@ -39,7 +39,7 @@ jobs:
   eslint:
     runs-on: ubuntu-latest
     steps:
-    - uses: actions/checkout@v3
+    - uses: actions/checkout@v2
     - uses: bradennapier/eslint-plus-action@v3
 ```
 
@@ -121,7 +121,7 @@ jobs:
   lint:
     runs-on: ubuntu-latest
     steps:
-    - uses: actions/checkout@v3
+    - uses: actions/checkout@v2
     - uses: bradennapier/eslint-plus-action@v3
 ```
 
@@ -139,7 +139,7 @@ jobs:
   eslint:
     runs-on: ubuntu-latest
     steps:
-    - uses: actions/checkout@v3
+    - uses: actions/checkout@v2
     - uses: bradennapier/eslint-plus-action@v3
 ```
 
@@ -152,7 +152,7 @@ jobs:
   eslint:
     runs-on: ubuntu-latest
     steps:
-    - uses: actions/checkout@v3
+    - uses: actions/checkout@v2
     - uses: bradennapier/eslint-plus-action@v3
       env:
         NPM_TOKEN: ${{secrets.NPM_TOKEN}}
@@ -165,7 +165,7 @@ jobs:
   eslint:
     runs-on: ubuntu-latest
     steps:
-    - uses: actions/checkout@v3
+    - uses: actions/checkout@v2
     - uses: bradennapier/eslint-plus-action@v3
       env:
         NPM_TOKEN: ${{secrets.NPM_TOKEN}}