remove unnecessary file.

build/rollup-plugin-ec-dev.js

-/**
- * Define variable `__DEV__`.
- *
- * Usage:
- *
- * import ecDevPlugin from 'echats/build/rollup-plugin-ec-dev';
- * let rollupConfig = {
- *     plugins: [
- *         ecDevPlugin(),
- *         ...
- *     ]
- * };
- *
- * We use global variable `__DEV__` for convenience, but it bring trouble
- * while building: it is not able to make sure the decaration of `__DEV__`
- * occures in front of the whole code if we use ES module import. So we
- * use the plugin to handle that.
- *
- * See `echarts/src/config.js`.
- */
-
-module.exports = function (opt) {
-
-    return {
-        intro: function () {
-            return [
-                'if (typeof __DEV__ === "undefined") {',
-                '    if (typeof window !== "undefined") {',
-                '        window.__DEV__ = true;',
-                '    }',
-                '    else if (typeof global !== "undefined") {',
-                '        global.__DEV__ = true;',
-                '    }',
-                '}'
-            ].join('\n');
-        }
-    };
-};