Update copy on branch discovery to not imply deprecation. (#306)

Author: behoyh

src/main/resources/com/cloudbees/jenkins/plugins/bitbucket/BranchDiscoveryTrait/help-strategyId.html

@@ -8,8 +8,8 @@
         </dd>
         <dt>Only branches that are also filed as PRs</dt>
         <dd>
-            This option exists to preserve legacy behaviour when upgrading from older versions of the plugin.
-            NOTE: If you have an actual use case for this option please file a pull request against this text.
+            Discovers branches that have PR's associated with them. This may make sense if you have a 
+            notification sent to the team at the end of a triggered build or limited Jenkins resources. 
         </dd>
         <dt>All branches</dt>
         <dd>