Get rid of inheritence on Vector4 struct to prevent offsetof macro giving out a warning on gcc

src/Common/Game/T6/T6_Assets.h

@@ -3594,7 +3594,6 @@ namespace T6
         unsigned int m128_u32[4];
     };
 
-
     struct vector3
     {
         __m128 x;
@@ -3602,9 +3601,11 @@ namespace T6
         __m128 z;
     };
 
-
+    struct vector4
-    struct vector4 : vector3
     {
+        __m128 x;
+        __m128 y;
+        __m128 z;
         __m128 w;
     };