Fix grammar of wrong browser message (#376)

cvat/apps/engine/static/engine/js/checkPlatform.js

@@ -13,8 +13,8 @@
 var supportedPlatforms = ['Chrome'];
 if (supportedPlatforms.indexOf(platform.name) == -1) {
     try {
-        document.documentElement.innerHTML = "<center><h1> You browser detected as " + platform.name +
-        ". This tool not supports it. Please use latest version of Google Chrome.</h1></center>";
+        document.documentElement.innerHTML = "<center><h1> Your browser is detected as " + platform.name +
+        ". This tool does not support it. Please use the latest version of Google Chrome.</h1></center>";
         window.stop();
     }
     catch (err) {