idmap2: fix clang-tidy warnings [modernize-*]

Bug: 120024673
Test: mmm frameworks/base/cmds/idmap2; check output
Change-Id: I8768169fb7b541eb6b1aa3311c46a710eb71aac9
diff --git a/cmds/idmap2/tests/XmlTests.cpp b/cmds/idmap2/tests/XmlTests.cpp
index 40758b42..fe79d8f 100644
--- a/cmds/idmap2/tests/XmlTests.cpp
+++ b/cmds/idmap2/tests/XmlTests.cpp
@@ -27,8 +27,7 @@
 using ::testing::IsNull;
 using ::testing::NotNull;
 
-namespace android {
-namespace idmap2 {
+namespace android::idmap2 {
 
 TEST(XmlTests, Create) {
   auto zip = ZipFile::Open(GetTestDataPath() + "/target/target.apk");
@@ -68,5 +67,4 @@
   ASSERT_THAT(fail, IsNull());
 }
 
-}  // namespace idmap2
-}  // namespace android
+}  // namespace android::idmap2