gn: Fix some typos in unittests.

tools/gn/substitution_writer_unittest.cc

Index: tools/gn/substitution_writer_unittest.cc
diff --git a/tools/gn/substitution_writer_unittest.cc b/tools/gn/substitution_writer_unittest.cc
index 6542f77e0bc3bd7c733a9b40e5ce40cb43d4e4db..264dcea2444635c2565e9465322d7de928ad056a 100644
--- a/tools/gn/substitution_writer_unittest.cc
+++ b/tools/gn/substitution_writer_unittest.cc
@@ -59,7 +59,7 @@ TEST(SubstitutionWriter, ApplyPatternToSourceAsOutputFile) {
   ASSERT_EQ("gen/foo/bar/myfile.tmp", result.value());
 }
 
-TEST(SubstutitionWriter, WriteNinjaVariablesForSource) {
+TEST(SubstitutionWriter, WriteNinjaVariablesForSource) {
   TestWithScope setup;
 
   std::vector<SubstitutionType> types;
@@ -101,7 +101,7 @@ TEST(SubstitutionWriter, WriteWithNinjaVariables) {
       out.str());
 }
 
-TEST(SubstutitionWriter, SourceSubstitutions) {
+TEST(SubstitutionWriter, SourceSubstitutions) {
   TestWithScope setup;
 
   // Call to get substitutions relative to the build dir.