Restore unused block warnings condition for Ruby 3.4

ruby/ruby#10403 raised many "the block passed to" warnings.
then idnored these warnings because some of them might have contain false positives.

Now we can restore the warning condition
because these false positives should have been addressed by these changes:

ruby/ruby#10559
rails#51597
rails#51583

activesupport/lib/active_support/testing/strict_warnings.rb

@@ -14,10 +14,6 @@ class WarningError < StandardError; end
       # Expected non-verbose warning emitted by Rails.
       /Ignoring .*\.yml because it has expired/,
       /Failed to validate the schema cache because/,
-
-      # Ref: https://bugs.ruby-lang.org/issues/15554
-      # This new Ruby 3.4 warning is still being fined tuned to reduce false positives
-      /the block passed to/,
     )
 
     SUPPRESSED_WARNINGS = Regexp.union(