Analysis: use pull_request_target

Can't post reports otherwise as github token is readonly in pull_request

Signed-off-by: Álvaro Brey Vilas <alvaro.brey@nextcloud.com>

.github/workflows/analysis.yml

@@ -1,7 +1,7 @@
 name: "Analysis"
 
 on:
-    pull_request:
+    pull_request_target:
         branches: [ master, stable-* ]
     push:
         branches: [ master, stable-* ]