Bump rszr from 0.4.0 to 0.5.2

Bumps [rszr](https://github.com/mtgrosser/rszr) from 0.4.0 to 0.5.2.
- [Release notes](https://github.com/mtgrosser/rszr/releases)
- [Changelog](https://github.com/mtgrosser/rszr/blob/master/CHANGELOG.md)
- [Commits](https://github.com/mtgrosser/rszr/compare/v0.4.0...v0.5.2)

Gemfile

@@ -123,7 +123,7 @@ gem 'rubyntlm', git: 'https://github.com/wimm/rubyntlm'
 gem 'viewpoint'
 
 # image processing
-gem 'rszr', '0.4.0'
+gem 'rszr', '0.5.2'
 
 # Gems used only for develop/test and not required
 # in production environments by default.

Gemfile.lock

@@ -425,7 +425,7 @@ GEM
       rspec-mocks (~> 3.8.0)
       rspec-support (~> 3.8.0)
     rspec-support (3.8.0)
-    rszr (0.4.0)
+    rszr (0.5.2)
     rubocop (0.67.2)
       jaro_winkler (~> 1.5.1)
       parallel (~> 1.10)
@@ -609,7 +609,7 @@ DEPENDENCIES
   rb-fsevent
   rchardet (>= 1.8.0)
   rspec-rails
-  rszr (= 0.4.0)
+  rszr (= 0.5.2)
   rubocop
   rubocop-performance
   rubocop-rspec

app/models/store.rb

@@ -281,10 +281,6 @@ returns
     file.provider
   end
 
-  def self.semaphore
-    @semaphore ||= Mutex.new
-  end
-
   private
 
   def image_resize(content, width)
@@ -299,25 +295,19 @@ returns
     temp_file.binmode
     temp_file.write(content)
     temp_file.close
+    image = Rszr::Image.load(temp_file.path)
 
-    temp_file_resize = nil
-    self.class.semaphore.synchronize do
-      image = Rszr::Image.load(temp_file.path)
-
-      # do not resize image if image is smaller or already same size
-      return if image.width <= width
+    # do not resize image if image is smaller or already same size
+    return if image.width <= width
 
-      # do not resize image if new height is smaller then 7px (images
-      # with small height are usally usefull to resize)
-      ratio = image.width / width
-      return if image.height / ratio <= 6
-
-      image.resize!(width, :auto)
-      temp_file_resize = ::Tempfile.new.path
-      image.save(temp_file_resize)
-      image.send(:handle).finalize!
-    end
+    # do not resize image if new height is smaller then 7px (images
+    # with small height are usally usefull to resize)
+    ratio = image.width / width
+    return if image.height / ratio <= 6
 
+    image.resize!(width, :auto)
+    temp_file_resize = ::Tempfile.new.path
+    image.save(temp_file_resize)
     image_resized = ::File.binread(temp_file_resize)
 
     Cache.write(cache_key, image_resized, { expires_in: 6.months })