Remove unnecessary `explicit` qualifiers on constructors.

Change-Id: Id12e392ad50f66a6e2251a68662b7959315dc567
diff --git a/compiler/jni/quick/calling_convention.h b/compiler/jni/quick/calling_convention.h
index c9b595a..243d124 100644
--- a/compiler/jni/quick/calling_convention.h
+++ b/compiler/jni/quick/calling_convention.h
@@ -348,8 +348,8 @@
     kObjectOrClass = 1
   };
 
-  explicit JniCallingConvention(bool is_static, bool is_synchronized, const char* shorty,
-                                size_t frame_pointer_size)
+  JniCallingConvention(bool is_static, bool is_synchronized, const char* shorty,
+                       size_t frame_pointer_size)
       : CallingConvention(is_static, is_synchronized, shorty, frame_pointer_size) {}
 
   // Number of stack slots for outgoing arguments, above which the handle scope is