style: add missing eslint no-undef directive to ndarray/colcat Examples block

Matches the convention used across every other @stdlib/ndarray
top-level README.

Author: claude

lib/node_modules/@stdlib/ndarray/colcat/README.md

@@ -111,6 +111,8 @@ The function accepts the following arguments:
 
 ## Examples
 
+<!-- eslint no-undef: "error" -->
+
 ```javascript
 var discreteUniform = require( '@stdlib/random/discrete-uniform' );
 var ndarray2array = require( '@stdlib/ndarray/to-array' );