Fix grammar

wiki/src/contribute/working_together/roles/technical_writer.mdwn

@@ -14,7 +14,7 @@ as a fallback if no other contributor volunteers to do it.
   - Redacting exceptional publications on our
     blog (security advisory, etc.) or reviewing
     them against our style guide.
-  - Reviewing contributions of paid workers to our end-user
+  - Reviewing contributions by paid workers to our end-user
     documentation (/doc and /support) against our style guide.
     For example, the [[Foundations Team]]
     sometimes writes known issues.