Remove 'interface' from check_filename error msg.

This can be referring to an interface or to a
parcelable, so it is less confusing to remove this.

Bug: N/A
Test: trigger error
Change-Id: I753e1f406c8c10549f01b26460c033635eb76ccb
diff --git a/aidl.cpp b/aidl.cpp
index 88a42f8..5cc186f 100644
--- a/aidl.cpp
+++ b/aidl.cpp
@@ -125,8 +125,7 @@
     }
 
     if (!valid) {
-        fprintf(stderr, "%s:%d interface %s should be declared in a file"
-                " called %s.\n",
+        fprintf(stderr, "%s:%d %s should be declared in a file called %s.\n",
                 filename.c_str(), line, name.c_str(), expected.c_str());
     }