Fix terminology: use 'testsuite' instead of 'test suite'

Co-authored-by: butako <[email protected]>

Author: Copilot

tests/functional/testplan/testing/multitest/test_default_testcase_timeout.py

@@ -15,7 +15,7 @@
 
 @testsuite
 class SuiteWithoutTimeout:
-    """Test suite with testcases that don't have explicit timeout."""
+    """Testsuite with testcases that don't have explicit timeout."""
 
     @testcase
     def test_passes_quickly(self, env, result):
@@ -31,7 +31,7 @@ def test_takes_time(self, env, result):
 
 @testsuite
 class SuiteWithExplicitTimeout:
-    """Test suite with testcases that have explicit timeout."""
+    """Testsuite with testcases that have explicit timeout."""
 
     @testcase(timeout=5)
     def test_with_explicit_timeout(self, env, result):