Resolve the following technical debt issues: misc-unused-using-decls

CL generated via Upkeep (go/upkeep).

#upkeep #autofix #codehealth #cleanup

Tested:
    Local presubmit tests passed.
PiperOrigin-RevId: 738031266
diff --git a/quiche/http2/adapter/adapter_impl_comparison_test.cc b/quiche/http2/adapter/adapter_impl_comparison_test.cc
index e85835a..ac20723 100644
--- a/quiche/http2/adapter/adapter_impl_comparison_test.cc
+++ b/quiche/http2/adapter/adapter_impl_comparison_test.cc
@@ -19,7 +19,6 @@
 
 using ::testing::_;
 using ::testing::AssertionResult;
-using ::testing::Each;
 using ::testing::InvokeWithoutArgs;
 
 enum FrameType {
diff --git a/quiche/http2/adapter/noop_header_validator_test.cc b/quiche/http2/adapter/noop_header_validator_test.cc
index 000c2df..ce94440 100644
--- a/quiche/http2/adapter/noop_header_validator_test.cc
+++ b/quiche/http2/adapter/noop_header_validator_test.cc
@@ -12,8 +12,6 @@
 namespace adapter {
 namespace test {
 
-using ::testing::Optional;
-
 using Header = std::pair<absl::string_view, absl::string_view>;
 constexpr Header kSampleRequestPseudoheaders[] = {{":authority", "www.foo.com"},
                                                   {":method", "GET"},