Use Wuffs v0.3 by default, not v0.2

This is roll-forward of
https://skia-review.googlesource.com/c/skia/+/298616/

Change-Id: I44d65dcb67555fd76075e2d415d96db82c376cae
Reviewed-on: https://skia-review.googlesource.com/c/skia/+/301756
Commit-Queue: Leon Scroggins <scroggo@google.com>
Reviewed-by: Leon Scroggins <scroggo@google.com>

BUILD.gn

@@ -906,6 +906,7 @@ optional("wuffs") {
   enabled = skia_use_wuffs
   public_defines = [
     "SK_HAS_WUFFS_LIBRARY",
+
     # SK_FAVOR_WUFFS_V_0_3_OVER_V_0_2 is temporary, used during a multiple step
     # transition (perhaps a month or two in mid 2020), distributed across
     # multiple repositories:
@@ -924,10 +925,7 @@ optional("wuffs") {
     # Steps 2a and 2b can occur concurrently. Similarly for 3a and 3b.
     #
     # "Users" means software that uses Skia+Wuffs, such as Chromium or Flutter.
-    #
-    # Uncommenting the next line (as well as changing "0.2" to "0.3" in
-    # "etc/wuffs-v0.2.c" in third_party/wuffs/BUILD.gn) is step 3b.
-    # "SK_FAVOR_WUFFS_V_0_3_OVER_V_0_2",
+    "SK_FAVOR_WUFFS_V_0_3_OVER_V_0_2",
   ]
 
   deps = [ "//third_party/wuffs" ]

third_party/wuffs/BUILD.gn

@@ -45,5 +45,5 @@ third_party("wuffs") {
     "WUFFS_CONFIG__MODULE__LZW",
   ]
 
-  sources = [ "../externals/wuffs/release/c/wuffs-v0.2.c" ]
+  sources = [ "../externals/wuffs/release/c/wuffs-v0.3.c" ]
 }