[core] Remove obsolete modular arithmetic on atlas coordinates

We switched to 16-bit coordinates in attributes in b0cb8715ed, so there's no longer any reason to require that they are divisible by four.

src/mbgl/programs/symbol_program.cpp

@@ -51,7 +51,7 @@ Values makeValues(const bool isText,
                                    values.translateAnchor,
                                    state) },
         uniforms::u_extrude_scale::Value{ extrudeScale },
-        uniforms::u_texsize::Value{ std::array<float, 2> {{ float(texsize.width) / 4, float(texsize.height) / 4 }} },
+        uniforms::u_texsize::Value{ std::array<float, 2> {{ float(texsize.width), float(texsize.height) }} },
         uniforms::u_zoom::Value{ float(state.getZoom()) },
         uniforms::u_rotate_with_map::Value{ values.rotationAlignment == AlignmentType::Map },
         uniforms::u_texture::Value{ 0 },