add missing space

Author: ifxfrancois

tests/run-make/rustdoc-default-output/output-default.stdout

@@ -170,7 +170,7 @@ Options:
         --scrape-examples-target-crate collect function call information for functions from the target crate
 
         --scrape-tests  Include test code when scraping examples
-        --document-tests
+        --document-tests 
                         Generate documentation for tests
         --with-examples path to function call information (for displaying examples in the documentation)