Bump xterm from 4.14.1 to 4.15.0 (#4510)

Co-authored-by: dependabot[bot] <49699333+dependabot[bot]@users.noreply.github.com>

package.json

@@ -393,7 +393,7 @@
     "webpack-cli": "^3.3.12",
     "webpack-dev-server": "^3.11.3",
     "webpack-node-externals": "^1.7.2",
-    "xterm": "^4.14.1",
+    "xterm": "^4.15.0",
     "xterm-addon-fit": "^0.5.0"
   }
 }