tools: no trailing slash in ignore patterns

Makes eslint exclude directories without enumerating their content

PR-URL: nodejs/node#16372
Refs: nodejs/node#16010
Refs: nodejs/node#16278
Reviewed-By: Rich Trott <rtrott@gmail.com>
Reviewed-By: Joyee Cheung <joyeec9h3@gmail.com>
Reviewed-By: Luigi Pinca <luigipinca@gmail.com>
Reviewed-By: Gibson Fahnestock <gibfahn@gmail.com>
Reviewed-By: James M Snell <jasnell@gmail.com>

.eslintignore

@@ -1,10 +1,10 @@
 lib/internal/v8_prof_polyfill.js
 lib/punycode.js
-test/addons/??_*/
+test/addons/??_*
 test/fixtures
-test/tmp*/
+test/tmp*
 tools/eslint
 tools/icu
 node_modules
-benchmark/tmp/
+benchmark/tmp
 doc/**/*.js