Revert GlobalState caching in ExpectationsTestRunner

GlobalState.new only costs ~2ms. Caching it had no measurable impact
on test duration and introduced shared mutable state across tests
within the same class.

Author: st0012

test/requests/support/expectations_test_runner.rb

@@ -8,14 +8,10 @@ class ExpectationsTestRunner < Minitest::Test
   TEST_PRISM_FIXTURES = File.join(TEST_FIXTURES_DIR, "prism/test/prism/fixtures/**", "*.txt")
 
   def setup
-    @global_state = self.class.shared_global_state
+    @global_state = RubyLsp::GlobalState.new
   end
 
   class << self
-    def shared_global_state
-      @shared_global_state ||= RubyLsp::GlobalState.new
-    end
-
     def expectations_tests(handler_class, expectation_suffix)
       class_eval(<<~RB, __FILE__, __LINE__ + 1)
         module ExpectationsRunnerMethods