Apply automatic rubocop fixes

app/models/tag.rb

@@ -1,22 +1,22 @@
-class Tag < ApplicationRecord
+# frozen_string_literal: true
 
+class Tag < ApplicationRecord
   has_many :exercise_tags
   has_many :exercises, through: :exercise_tags
 
-  validates_uniqueness_of :name
+  validates :name, uniqueness: true
 
   def destroy
-    if (can_be_destroyed?)
+    if can_be_destroyed?
       super
     end
   end
 
   def can_be_destroyed?
-    !exercises.any?
+    exercises.none?
   end
 
   def to_s
     name
   end
-
-end
+end