Don't disable WebP when compiling small binaries in Optimizing for size

WebP decoding is now required in pretty much any project since Godot 3.4
(unless you force PNG for lossless textures in the Project Settings).

Therefore, it's not a good idea to recommend disabling it for most
people. Not to mention the added binary size will be outweighted by
the smaller lossless WebPs most of the time.

development/compiling/optimizing_for_size.rst

@@ -63,7 +63,7 @@ a lot of them:
 
 ::
 
-    scons p=windows target=release tools=no module_arkit_enabled=no module_assimp_enabled=no module_bmp_enabled=no module_bullet_enabled=no module_camera_enabled=no module_csg_enabled=no module_dds_enabled=no module_enet_enabled=no module_etc_enabled=no module_gdnative_enabled=no module_gridmap_enabled=no module_hdr_enabled=no module_jsonrpc_enabled=no module_mbedtls_enabled=no module_mobile_vr_enabled=no module_opensimplex_enabled=no module_opus_enabled=no module_pvr_enabled=no module_recast_enabled=no module_regex_enabled=no module_squish_enabled=no module_svg_enabled=no module_tga_enabled=no module_theora_enabled=no module_tinyexr_enabled=no module_upnp_enabled=no module_vhacd_enabled=no module_vorbis_enabled=no module_webm_enabled=no module_webp_enabled=no module_webrtc_enabled=no module_websocket_enabled=no module_xatlas_unwrap_enabled=no
+    scons p=windows target=release tools=no module_arkit_enabled=no module_assimp_enabled=no module_bmp_enabled=no module_bullet_enabled=no module_camera_enabled=no module_csg_enabled=no module_dds_enabled=no module_enet_enabled=no module_etc_enabled=no module_gdnative_enabled=no module_gridmap_enabled=no module_hdr_enabled=no module_jsonrpc_enabled=no module_mbedtls_enabled=no module_mobile_vr_enabled=no module_opensimplex_enabled=no module_opus_enabled=no module_pvr_enabled=no module_recast_enabled=no module_regex_enabled=no module_squish_enabled=no module_svg_enabled=no module_tga_enabled=no module_theora_enabled=no module_tinyexr_enabled=no module_upnp_enabled=no module_vhacd_enabled=no module_vorbis_enabled=no module_webm_enabled=no module_webrtc_enabled=no module_websocket_enabled=no module_xatlas_unwrap_enabled=no
 
 If this proves not to work for your use case, you should review the list of
 modules and see which ones you actually still need for your game (e.g. you
@@ -107,7 +107,6 @@ following:
     module_vhacd_enabled = "no"
     module_vorbis_enabled = "no"
     module_webm_enabled = "no"
-    module_webp_enabled = "no"
     module_webrtc_enabled = "no"
     module_websocket_enabled = "no"
     module_xatlas_unwrap_enabled = "no"