Redundant message fix (#143978)

Saying that the commands only work on macOS is redundant because the command is only shown on macOS hosts.

Author: ShrootBuck

packages/flutter_tools/lib/src/commands/build_ios.dart

@@ -52,7 +52,7 @@ class BuildIOSCommand extends _BuildIOSSubCommand {
   final String name = 'ios';
 
   @override
-  final String description = 'Build an iOS application bundle (macOS host only).';
+  final String description = 'Build an iOS application bundle.';
 
   @override
   final XcodeBuildAction xcodeBuildAction = XcodeBuildAction.build;
@@ -129,7 +129,7 @@ class BuildIOSArchiveCommand extends _BuildIOSSubCommand {
   final List<String> aliases = <String>['xcarchive'];
 
   @override
-  final String description = 'Build an iOS archive bundle and IPA for distribution (macOS host only).';
+  final String description = 'Build an iOS archive bundle and IPA for distribution.';
 
   @override
   final XcodeBuildAction xcodeBuildAction = XcodeBuildAction.archive;