Refactor tmpl and blob_excerpt (#32967)

1. do not use `{{/* */}}` to remove spaces, use `{{- -}}`
2. fix "blob_excerpt" endpoint, remove the legacy fragile code: have
tested commit diff and wiki diff

templates/repo/issue/view_content/pull.tmpl

@@ -367,8 +367,7 @@
 				{{end}}
 			{{end}}{{/* end if: pull request status */}}
 
-			{{/*
-			Manually Merged is not a well-known feature, it is used to mark a non-mergeable PR (already merged, conflicted) as merged
+			{{/* Manually Merged is not a well-known feature, it is used to mark a non-mergeable PR (already merged, conflicted) as merged
 			To test it:
 			* Enable "Manually Merged" feature in the Repository Settings
 			* Create a pull request, either: