Make model sanitization methods one liners

CHANGELOG

@@ -10,6 +10,7 @@ v 8.8.0 (unreleased)
   - Add 'l' shortcut to open Label dropdown on issuables and 'i' to create new issue on a project
   - Updated search UI
   - Display informative message when new milestone is created
+  - Sanitize milestones and labels titles
   - Allow "NEWS" and "CHANGES" as alternative names for CHANGELOG. !3768 (Connor Shea)
   - Added button to toggle whitespaces changes on diff view
   - Backport GitLab Enterprise support from EE

app/models/label.rb

@@ -117,9 +117,8 @@ def text_color
     LabelsHelper::text_color_for_bg(self.color)
   end
 
-  def title= value
-    value = Sanitize.clean(value.to_s) if value
-    write_attribute(:title, Sanitize.clean(value))
+  def title=(value)
+    write_attribute(:title, Sanitize.clean(value.to_s)) if value.present?
   end
 
   private

app/models/milestone.rb

@@ -129,9 +129,8 @@ def author_id
     nil
   end
 
-  def title= value
-    value = Sanitize.clean(value.to_s) if value
-    write_attribute(:title, value)
+  def title=(value)
+    write_attribute(:title, Sanitize.clean(value.to_s)) if value.present?
   end
 
   # Sorts the issues for the given IDs.