fix Lite gen title (Azure#40177)

Author: XiaofeiCao

eng/mgmt/automation/generation.yml

@@ -62,7 +62,7 @@ steps:
 - template: /eng/common/pipelines/templates/steps/create-pull-request.yml
   parameters:
     PRBranchName: fluent-lite-generation-$(Build.BuildId)
-    ${{ if variables.fromTypeSpec }}:
+    ${{ if eq(variables.fromTypeSpec, true) }}:
       CommitMsg: '[Automation] Generate Fluent Lite from TypeSpec $(README)'
       PRTitle: '[Automation] Generate Fluent Lite from TypeSpec $(README)'
     ${{ else }}: