[browser] Fix _XHarnessArgs property name in condition in tests.browser.targets (#97971)

Author: maraf

eng/testing/tests.browser.targets

@@ -104,7 +104,7 @@
 
     <_XHarnessArgs Condition="'$(IsFunctionalTest)' == 'true'"     >$(_XHarnessArgs) --expected-exit-code=$(ExpectedExitCode)</_XHarnessArgs>
     <_XHarnessArgs Condition="'$(WasmXHarnessArgs)' != ''"         >$(_XHarnessArgs) $(WasmXHarnessArgs)</_XHarnessArgs>
-    <_XHarnessArgs Condition="'$(WasmEnableThreads)' == 'true' and '$(_XHarnessArs.Contains(&quot;--web-server-use-cop&quot;)' != 'true'">$(_XHarnessArgs) --web-server-use-cop</_XHarnessArgs>
+    <_XHarnessArgs Condition="'$(WasmEnableThreads)' == 'true' and '$(_XHarnessArgs.Contains(&quot;--web-server-use-cop&quot;)' != 'true'">$(_XHarnessArgs) --web-server-use-cop</_XHarnessArgs>
     <_XHarnessArgs                                                 >$(_XHarnessArgs) -s dotnet.native.js.symbols</_XHarnessArgs>
     <_XHarnessArgs Condition="'$(_UseWasmSymbolicator)' == 'true'" >$(_XHarnessArgs) --symbol-patterns wasm-symbol-patterns.txt</_XHarnessArgs>
     <_XHarnessArgs Condition="'$(_UseWasmSymbolicator)' == 'true'" >$(_XHarnessArgs) --symbolicator WasmSymbolicator.dll,Microsoft.WebAssembly.Internal.SymbolicatorWrapperForXHarness</_XHarnessArgs>