Merge branch 'fix-any-milestone-value' into 'master'

Fixes issue with any milestone value in dropdown not being selectable

Closes #14293

See merge request !3234

app/assets/javascripts/milestone_select.js.coffee

@@ -30,6 +30,7 @@ class @MilestoneSelect
 
             if showAny
               data.unshift(
+                isAny: true
                 title: 'Any Milestone'
               )
 
@@ -46,7 +47,7 @@ class @MilestoneSelect
           milestone.title
         id: (milestone) ->
           if !useId
-            if milestone.title isnt "Any milestone"
+            if !milestone.isAny?
               milestone.title
             else
               ""