Remove babelcheck

Nobody is likley to be upgrading from babel 5 any more, so this
can go away now.

scripts/babelcheck.js

@@ -1,26 +0,0 @@
-#!/usr/bin/env node
-
-var exec = require('child_process').exec;
-
-// Makes sure the babel executable in the path is babel 6 (or greater), not
-// babel 5, which it is if you upgrade from an older version of react-sdk and
-// run 'npm install' since the package has changed to babel-cli, so 'babel'
-// remains installed and the executable in node_modules/.bin remains as babel
-// 5.
-
-// This script is duplicated from matrix-react-sdk because it can't reliably
-// be pulled in from react-sdk while npm install is failing, as it will do
-// if the environment is in the erroneous state this script checks for.
-
-exec("babel -V", function (error, stdout, stderr) {
-    if ((error && error.code) || parseInt(stdout.substr(0,1), 10) < 6) {
-        console.log("\033[31m\033[1m"+
-            '*****************************************\n'+
-            '* vector-web has moved to babel 6       *\n'+
-            '* Please "rm -rf node_modules && npm i" *\n'+
-            '* then restore links as appropriate     *\n'+
-            '*****************************************\n'+
-        "\033[91m");
-        process.exit(1);
-    }
-});