Fix memory leak caused by caching all unique paths seen

This optimisation was introduced in #2002. If an api's paths include
an id in the path then this cache can grow in an unbounded manner.

CHANGELOG.md

@@ -6,6 +6,7 @@
 * [#2060](https://github.com/ruby-grape/grape/pull/2060): Drop support for Ruby 2.4 - [@dblock](https://github.com/dblock).
 * [#2060](https://github.com/ruby-grape/grape/pull/2060): Upgraded Rubocop to 0.84.0 - [@dblock](https://github.com/dblock).
 * [#2077](https://github.com/ruby-grape/grape/pull/2077): Simplify logic for defining declared params - [@dnesteryuk](https://github.com/dnesteryuk).
+* [#2084](https://github.com/ruby-grape/grape/pull/2084): Fix memory leak in path normalization - [@fcheung](https://github.com/fcheung).
 * Your contribution here.
 
 #### Fixes

lib/grape/router.rb

@@ -7,20 +7,12 @@ module Grape
   class Router
     attr_reader :map, :compiled
 
-    class NormalizePathCache < Grape::Util::Cache
-      def initialize
-        @cache = Hash.new do |h, path|
-          normalized_path = +"/#{path}"
-          normalized_path.squeeze!('/')
-          normalized_path.sub!(%r{/+\Z}, '')
-          normalized_path = '/' if normalized_path.empty?
-          h[path] = -normalized_path
-        end
-      end
-    end
-
     def self.normalize_path(path)
-      NormalizePathCache[path]
+      path = +"/#{path}"
+      path.squeeze!('/')
+      path.sub!(%r{/+\Z}, '')
+      path = '/' if path == ''
+      path
     end
 
     def self.supported_methods