Export RunBp2BuildTestCaseSimple() in testing.go

This is to support the migration of conversion tests to be next
to the files they're testing

Bug: 242070498
Test: m bp2build
Change-Id: I66243d420743273e7ebad70886cfe690740182c4
diff --git a/bp2build/python_library_conversion_test.go b/bp2build/python_library_conversion_test.go
index 58587a6..a53371d 100644
--- a/bp2build/python_library_conversion_test.go
+++ b/bp2build/python_library_conversion_test.go
@@ -66,7 +66,7 @@
 	testCase.ModuleTypeUnderTest = "python_library"
 	testCase.ModuleTypeUnderTestFactory = python.PythonLibraryFactory
 
-	runBp2BuildTestCaseSimple(t, testCase)
+	RunBp2BuildTestCaseSimple(t, testCase)
 }
 
 func runPythonLibraryHostTestCase(t *testing.T, tc pythonLibBp2BuildTestCase) {