Revert "chore: read ESLINT_MOCHA_TIMEOUT env var in Makefile.js (es…

…lint#15626)"

This reverts commit d5eae6d.

Makefile.js

@@ -79,7 +79,7 @@ const NODE = "node ", // intentional extra space
     PERF_MULTIFILES_TARGETS = `"${PERF_MULTIFILES_TARGET_DIR + path.sep}{lib,tests${path.sep}lib}${path.sep}**${path.sep}*.js"`,
 
     // Settings
-    MOCHA_TIMEOUT = parseInt(process.env.ESLINT_MOCHA_TIMEOUT, 10) || 10000;
+    MOCHA_TIMEOUT = 10000;
 
 //------------------------------------------------------------------------------
 // Helpers

docs/developer-guide/unit-tests.md

@@ -37,7 +37,3 @@ Running individual tests is useful when you're working on a specific bug and ite
 ## More Control on Unit Testing
 
 `npm run test:cli` is an alias of the Mocha cli in `./node_modules/.bin/mocha`. [Options](https://mochajs.org/#command-line-usage) are available to be provided to help to better control the test to run.
-
-The default timeout for tests in `npm test` is 10000ms. You may change the timeout by providing `ESLINT_MOCHA_TIMEOUT` environment variable, for example:
-
-    ESLINT_MOCHA_TIMEOUT=20000 npm test