Fix typo

Change-Id: I3883dedde0ad3ca6c4d6190d711af9c1e6411a50
Reviewed-on: https://gerrit.libreoffice.org/73573
Tested-by: Jenkins
Reviewed-by: Julien Nabet <serval2412@yahoo.fr>

forms/source/inc/formnavigation.hxx

@@ -190,7 +190,7 @@ namespace frm
         */
         static const char* getFeatureURLAscii( sal_Int16 _nFeatureId );
 
-        /** retrieves the feature URL belonging to an feature id
+        /** retrieves the feature URL belonging to a feature id
 
             @complexity O(log n), with n being the number of all potentially known URLs
             @return
@@ -199,7 +199,7 @@ namespace frm
         */
         bool        getFeatureURL( sal_Int16 _nFeatureId, css::util::URL& /* [out] */ _rURL );
 
-        /** retrieves the feature id belonging to an feature URL
+        /** retrieves the feature id belonging to a feature URL
 
             @complexity O(n), with n being the number of all potentially known URLs
             @return