Allow running sorbet workflow manually.

.github/workflows/sorbet.yml

@@ -1,4 +1,5 @@
 name: Update Sorbet files
+
 on:
   push:
     paths:
@@ -7,6 +8,8 @@ on:
       - master
   schedule:
     - cron: '0 0 * * *'
+  workflow_dispatch:
+
 jobs:
   tapioca:
     if: github.repository == 'Homebrew/brew'
@@ -21,7 +24,7 @@ jobs:
         with:
           username: BrewTestBot
 
-      - name: Update Tapioca definitions
+      - name: Update RBI files
         id: update
         run: |
           git fetch origin