chore(updatecli) add missing endline in contributing manifest pattern (#935)

Fixup of #934

Author: dduportal

updatecli/updatecli.d/contributing.yaml

@@ -54,7 +54,7 @@ targets:
     spec:
       file: CONTRIBUTING.md
       matchpattern: >-
-        (?s)(### Technical Requirements)(.*)(### Add.*)
+        (?s)(### Technical Requirements)(.*)(### Add.*)\n
       replacepattern: |
         $1
         <!-- This section is automatically generated by updatecli with the manifest ./updatecli/updatecli.d/contributing.yaml -->