[WASM] Update actions/checkout to v2

# Conflicts:
#	.github/workflows/manual-distribution.yml

Author: kateinoigakukun

.github/workflows/main.yml

@@ -27,7 +27,7 @@ jobs:
           sudo apt clean
           docker rmi $(docker image ls -aq)
           df -h
-      - uses: actions/checkout@v1
+      - uses: actions/checkout@v2
         with:
           path: swift
       - name: Prepare sccache timestamp
@@ -76,7 +76,7 @@ jobs:
           sudo apt clean
           docker rmi $(docker image ls -aq)
           df -h
-      - uses: actions/checkout@v1
+      - uses: actions/checkout@v2
         with:
           path: swift
       - name: Prepare sccache timestamp
@@ -112,7 +112,7 @@ jobs:
     runs-on: macos-10.15
 
     steps:
-      - uses: actions/checkout@v1
+      - uses: actions/checkout@v2
         with:
           path: swift
       - name: Prepare sccache timestamp

.github/workflows/nightly-distribution.yml

@@ -6,7 +6,7 @@ jobs:
   nightly-distribution:
     runs-on: macos-latest
     steps:
-      - uses: actions/checkout@v1
+      - uses: actions/checkout@v2
       - name: Setup keychain
         run: |
           echo "$DARWIN_TOOLCHAIN_APPLICATION_CERT_BASE64" | base64 --decode -o developerID_application.p12