Chore: remove concat-stream dependency (#10173)

We use the `concat-stream` module to get source text from stdin when the `--stdin` flag is used. However, getting text from stdin is a one-liner without `concat-stream`, so it's not necessary to keep it as a dependency.

bin/eslint.js

@@ -27,8 +27,7 @@ if (debug) {
 //------------------------------------------------------------------------------
 
 // now we can safely include the other modules that use debug
-const concat = require("concat-stream"),
-    cli = require("../lib/cli"),
+const cli = require("../lib/cli"),
     path = require("path"),
     fs = require("fs");
 
@@ -57,9 +56,7 @@ process.once("uncaughtException", err => {
 });
 
 if (useStdIn) {
-    process.stdin.pipe(concat({ encoding: "string" }, text => {
-        process.exitCode = cli.execute(process.argv, text);
-    }));
+    process.exitCode = cli.execute(process.argv, fs.readFileSync(process.stdin.fd, "utf8"));
 } else if (init) {
     const configInit = require("../lib/config/config-initializer");
 

package.json

@@ -37,7 +37,6 @@
     "ajv": "^6.0.1",
     "babel-code-frame": "^6.26.0",
     "chalk": "^2.1.0",
-    "concat-stream": "^1.6.2",
     "cross-spawn": "^6.0.5",
     "debug": "^3.1.0",
     "doctrine": "^2.1.0",