Fix repository_dispatch syntax (#56499)

Author: jakebailey

.github/workflows/new-release-branch.yaml

@@ -2,7 +2,7 @@ name: New Release Branch
 
 on:
   repository_dispatch:
-    types: new-release-branch
+    types: [new-release-branch]
 
 permissions:
   contents: read

.github/workflows/nightly.yaml

@@ -6,7 +6,7 @@ on:
   # enable users to manually trigger with workflow_dispatch
   workflow_dispatch: {}
   repository_dispatch:
-    types: publish-nightly
+    types: [publish-nightly]
 
 permissions:
   contents: read

.github/workflows/set-version.yaml

@@ -2,7 +2,7 @@ name: Set branch version
 
 on:
   repository_dispatch:
-    types: set-version
+    types: [set-version]
 
 permissions:
   contents: read

.github/workflows/sync-branch.yaml

@@ -2,7 +2,7 @@ name: Sync branch with master
 
 on:
   repository_dispatch:
-    types: sync-branch
+    types: [sync-branch]
   workflow_dispatch:
     inputs:
       branch_name:

.github/workflows/twoslash-repros.yaml

@@ -7,7 +7,7 @@ on:
   schedule:
     - cron: '0 8 * * *'
   repository_dispatch:
-    types: run-twoslash-repros
+    types: [run-twoslash-repros]
   workflow_dispatch:
     inputs:
       issue: