message: [SymbolFilePDB] Fix windows bots after rL367360
  SymbolFilePDB tests were using GetTypeSystemForLanguage but weren't
  changed to accomodate the use of an llvm::Expected. I adjusted them
  accordingly.
diff: @@ -390,8 +390,12 @@ TEST_F(SymbolFilePDBTests, TestNestedClassTypes) {
  llvm::DenseSet<SymbolFile *> searched_files;
  TypeMap results;
  - auto clang_ast_ctx = llvm::dyn_cast_or_null<ClangASTContext>(
  - symfile->GetTypeSystemForLanguage(lldb::eLanguageTypeC_plus_plus));
  + auto clang_ast_ctx_or_err =
  + symfile->GetTypeSystemForLanguage(lldb::eLanguageTypeC_plus_plus);
  + ASSERT_THAT_EXPECTED(clang_ast_ctx_or_err, llvm::Succeeded());
  +
  + auto clang_ast_ctx =
  + llvm::dyn_cast_or_null<ClangASTContext>(&clang_ast_ctx_or_err.get());
  EXPECT_NE(nullptr, clang_ast_ctx);
  EXPECT_EQ(1u, symfile->FindTypes(ConstString("Class"), nullptr, false, 0,
  @@ -440,8 +444,12 @@ TEST_F(SymbolFilePDBTests, TestClassInNamespace) {
  llvm::DenseSet<SymbolFile *> searched_files;
  TypeMap results;
  - auto clang_ast_ctx = llvm::dyn_cast_or_null<ClangASTContext>(
  - symfile->GetTypeSystemForLanguage(lldb::eLanguageTypeC_plus_plus));
  + auto clang_ast_ctx_or_err =
  + symfile->GetTypeSystemForLanguage(lldb::eLanguageTypeC_plus_plus);
  + ASSERT_THAT_EXPECTED(clang_ast_ctx_or_err, llvm::Succeeded());
  +
  + auto clang_ast_ctx =
  + llvm::dyn_cast_or_null<ClangASTContext>(&clang_ast_ctx_or_err.get());
  EXPECT_NE(nullptr, clang_ast_ctx);
  auto ast_ctx = clang_ast_ctx->getASTContext();
  