Fix markdown link in UPGRADING.md (#137)

Fixes the markdown link for `raw` docs.

UPGRADING.md

@@ -251,7 +251,7 @@ It's a common pattern in apps to inline small SVG files and low resolution versi
 Rails.application.assets.load_path.find('logo.svg').content
 ```
 
-As Rails escapes html tags in views by default, in order to output a rendered svg you will need to specify rails not to escape the string using [html_safe](https://api.rubyonrails.org/classes/String.html#method-i-html_safe) or [raw]((https://api.rubyonrails.org/classes/ActionView/Helpers/OutputSafetyHelper.html#method-i-raw).
+As Rails escapes html tags in views by default, in order to output a rendered svg you will need to specify rails not to escape the string using [html_safe](https://api.rubyonrails.org/classes/String.html#method-i-html_safe) or [raw](https://api.rubyonrails.org/classes/ActionView/Helpers/OutputSafetyHelper.html#method-i-raw).
 ```ruby
 Rails.application.assets.load_path.find('logo.svg').html_safe
 raw Rails.application.assets.load_path.find('logo.svg')
@@ -263,4 +263,4 @@ Propshaft uses a dynamic assets resolver in development mode. However, when you
 
 If you wish to have dynamic assets resolver enabled again, you need to clean your target folder (usually `public/assets`) and propshaft will start serving dynamic content from source.
 
-Another way to watch changes in your CSS & JS assets is by running `bin/dev` command instead of `rails server` that not only runs the server but also keeps looking for any changes in the assets and once it detects any changes, it compiles them while the server is running. This is possible because of the `Procfile.dev`.
+Another way to watch changes in your CSS & JS assets is by running `bin/dev` command instead of `rails server` that not only runs the server but also keeps looking for any changes in the assets and once it detects any changes, it compiles them while the server is running. This is possible because of the `Procfile.dev`.