fix typo

RELEASE_NOTES.txt

@@ -10,7 +10,7 @@ Release 1.5 (08/04/2017)
   - Processing for SDDS metadata in MongoDB cataloging plugin
   - Component Database processing plugin 
 - DM Station GUI fixes/enhancements:
-  - Fixed isses with DM_BEAMLINE_NAME not set
+  - Fixed issue with DM_BEAMLINE_NAME not set
   - Fixed issues with buttons that require previous item selection
   - Added start date to list of DAQs and uploads
   - Added ability to remove completed DAQs or uploads from the top-level list