Revert "Make lots of tests run in parallel"

This reverts commit 323dc60712.

Reason for revert: Possible cause of test instability
Bug: 170513220
Test: soong tests

Change-Id: Iee168e9fbb4210569e6cffcc23e60d111403abb8

androidmk/parser/parser_test.go

@@ -37,7 +37,6 @@ var parserTestCases = []struct {
 }
 
 func TestParse(t *testing.T) {
-	t.Parallel()
 	for _, test := range parserTestCases {
 		t.Run(test.name, func(t *testing.T) {
 			p := NewParser(test.name, bytes.NewBufferString(test.in))