tool/build/web: move source-maps CLI flag to "general" web section (#151722)

...now that wasm supports source maps (see flutter/flutter#151643)

Author: kevmoo

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

@@ -65,6 +65,12 @@ class BuildWebCommand extends BuildSubCommand {
       defaultsTo: '${WebCompilerConfig.kDefaultOptimizationLevel}',
       allowed: const <String>['0', '1', '2', '3', '4'],
     );
+    argParser.addFlag(
+      'source-maps',
+      help: 'Generate a sourcemap file. These can be used by browsers '
+            'to view and debug the original source code of a compiled and minified Dart '
+            'application.'
+    );
 
     //
     // JavaScript compilation options
@@ -75,12 +81,6 @@ class BuildWebCommand extends BuildSubCommand {
       help: 'Disable dynamic generation of code in the generated output. '
             'This is necessary to satisfy CSP restrictions (see http://www.w3.org/TR/CSP/).'
     );
-    argParser.addFlag(
-      'source-maps',
-      help: 'Generate a sourcemap file. These can be used by browsers '
-            'to view and debug the original source code of a compiled and minified Dart '
-            'application.'
-    );
     argParser.addOption('dart2js-optimization',
       help: 'Sets the optimization level used for Dart compilation to JavaScript. '
             'Deprecated: Please use "-O=<level>" / "--optimization-level=<level>".',