[Impeller] Turned on wide gamut support by default. (#39801) (#41965)

relands #39801

forward fix for internal customers at cl/531288297

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Author: gaaclarke

shell/platform/darwin/ios/framework/Source/FlutterDartProject.mm

@@ -156,10 +156,9 @@
   settings.may_insecurely_connect_to_all_domains = true;
   settings.domain_network_policy = "";
 
-  // Whether to enable Impeller.
+  // Whether to enable wide gamut colors.
   NSNumber* nsEnableWideGamut = [mainBundle objectForInfoDictionaryKey:@"FLTEnableWideGamut"];
-  // TODO(gaaclarke): Make this value `on` by default (pending memory audit).
-  BOOL enableWideGamut = nsEnableWideGamut ? nsEnableWideGamut.boolValue : NO;
+  BOOL enableWideGamut = nsEnableWideGamut ? nsEnableWideGamut.boolValue : YES;
   settings.enable_wide_gamut = enableWideGamut;
 
   // TODO(dnfield): We should reverse the order for all these settings so that command line options