Fix stripping Gem paths with Regexp characters

e.g. the 3.2 RC contains a '+' in the gem path (at least locally and on
CI): `/../.gem/ruby/3.2.0+3`

This needs escaping or it won't match any paths because it is expecting
1 or more '0' characters, rather than the literal characters '0+'

CHANGELOG.md

@@ -3,6 +3,11 @@ Changelog
 
 ## TBD
 
+### Fixes
+
+* Allow Gem paths to be stripped from file names in stacktraces when they contain a Regexp special character
+  | [#764](https://github.com/bugsnag/bugsnag-ruby/pull/764)
+
 ### Enhancements
 
 * Use `Exception#detailed_message` instead of `Exception#message` when available

lib/bugsnag/stacktrace.rb

@@ -48,7 +48,9 @@ def self.process(backtrace, configuration)
 
         # Strip common gem path prefixes
         if defined?(Gem)
-          file = Gem.path.inject(file) {|line, path| line.sub(/#{path}\//, "") }
+          Gem.path.each do |path|
+            file.sub!("#{path}/", "")
+          end
         end
 
         trace_hash[:file] = file