Exclude encryption performance tests from isolated runs

Encryption performance tests were meant to be excluded from the builds,
however they were still being executed when running `isolated:` tests
for active record adapters.

See https://buildkite.com/rails/rails/builds/76249#e7605d50-87be-445e-a9ae-a5761c996597/1512-1531

activerecord/Rakefile

@@ -112,7 +112,7 @@ end
         test_options = ENV["TESTOPTS"].to_s.split(/[\s]+/)
 
         test_files = (Dir["test/cases/**/*_test.rb"].reject {
-          |x| x.include?("/adapters/")
+          |x| x.include?("/adapters/") || x.include?("/encryption/performance")
         } + Dir["test/cases/adapters/#{adapter_short}/**/*_test.rb"]).sort
 
         if ENV["BUILDKITE_PARALLEL_JOB_COUNT"]