Remove ENABLE_PATH_CHECK workaround

Since Ruby 2.7, this warning is not emitted anymore
It was removed as part of https://bugs.ruby-lang.org/issues/16131

Here's the output of running `ENV['PATH']` against various ruby versions,
when `$PATH` contains a world-writable folder:

```
===============1.8.7-p374================
-e:1: warning: Insecure world writable dir /app/whatever in PATH, mode 040757
===============1.9.3-p551================
-e:1: warning: Insecure world writable dir /app/whatever in PATH, mode 040757
===============2.0.0-p648================
-e:1: warning: Insecure world writable dir /app/whatever in PATH, mode 040757
=================2.1.10==================
-e:1: warning: Insecure world writable dir /app/whatever in PATH, mode 040757
=================2.2.10==================
-e:1: warning: Insecure world writable dir /app/whatever in PATH, mode 040757
==================2.3.8==================
-e:1: warning: Insecure world writable dir /app/whatever in PATH, mode 040757
=================2.4.10==================
-e:1: warning: Insecure world writable dir /app/whatever in PATH, mode 040757
==================2.5.9==================
-e:1: warning: Insecure world writable dir /app/whatever in PATH, mode 040757
=================2.6.10==================
-e:1: warning: Insecure world writable dir /app/whatever in PATH, mode 040757
==================2.7.8==================
==================3.0.7==================
==================3.1.6==================
==================3.2.6==================
==================3.3.6==================
================3.4.0-rc1================
```

In https://bugs.ruby-lang.org/issues/20971, it was OKed to officially deprecate
since not emitting this was unintentional at the time

Author: Earlopain