Silence _perform method redefinition warning

I'd like to get rid of this noisy warning:

```shell
sentry-rails-5.26.0/lib/sentry/rails/background_worker.rb:5: warning: method redefined; discarding old _perform
sentry-ruby-5.26.0/lib/sentry/background_worker.rb:74: warning: previous definition of _perform was here
```

#skip-changelog

# Please enter the commit message for your changes. Lines starting
# with '#' will be kept; you may remove them yourself if you want to.
# An empty message aborts the commit.
#
# Date:      Sun Aug 24 01:04:29 2025 +0400
#
# On branch silence-perform-method-redefinition-warning
# Changes to be committed:
#	modified:   lib/sentry/rails/background_worker.rb
#

Author: viralpraxis

sentry-rails/lib/sentry/rails/background_worker.rb

@@ -2,6 +2,7 @@
 
 module Sentry
   class BackgroundWorker
+    alias :_perform :_perform # Silence method redefinition warning.
     def _perform(&block)
       block.call
     ensure