cpplint: Cleanup errors

Cleanup errors from upstream cpplint in preparation
for moving art's cpplint fork to upstream tip-of-tree cpplint.

Test: cd art && mm
Bug: 68951293
Change-Id: I15faed4594cbcb8399850f8bdee39d42c0c5b956
diff --git a/compiler/utils/label.h b/compiler/utils/label.h
index d835c63..b9d4e9c 100644
--- a/compiler/utils/label.h
+++ b/compiler/utils/label.h
@@ -27,23 +27,23 @@
 class AssemblerFixup;
 
 namespace arm64 {
-  class Arm64Assembler;
+class Arm64Assembler;
 }  // namespace arm64
 namespace mips {
-  class MipsAssembler;
-  class MipsLabel;
+class MipsAssembler;
+class MipsLabel;
 }  // namespace mips
 namespace mips64 {
-  class Mips64Assembler;
-  class Mips64Label;
+class Mips64Assembler;
+class Mips64Label;
 }  // namespace mips64
 namespace x86 {
-  class X86Assembler;
-  class NearLabel;
+class X86Assembler;
+class NearLabel;
 }  // namespace x86
 namespace x86_64 {
-  class X86_64Assembler;
-  class NearLabel;
+class X86_64Assembler;
+class NearLabel;
 }  // namespace x86_64
 
 class ExternalLabel {