style: replace isString with inline typeof check in ml/base/kmeans/algorithm-enum2str

Match the established enum2str pattern used by `blas/base/transpose-operation-enum2str`
and the other BLAS enum2str packages: drop the `@stdlib/assert/is-string`
import and use an inline `typeof v === 'string'` guard instead.

Author: claude

lib/node_modules/@stdlib/ml/base/kmeans/algorithm-enum2str/lib/main.js

@@ -20,7 +20,6 @@
 
 // MODULES //
 
-var isString = require( '@stdlib/assert/is-string' ).isPrimitive;
 var objectInverse = require( '@stdlib/object/inverse' );
 var enumeration = require( '@stdlib/ml/base/kmeans/algorithms' ).enum;
 
@@ -51,7 +50,7 @@ var hash = objectInverse( enumeration(), {
 */
 function enum2str( value ) {
 	var v = hash[ value ];
-	return ( isString( v ) ) ? v : null; // note: we include this guard to prevent walking the prototype chain
+	return ( typeof v === 'string' ) ? v : null; // note: we include this guard to prevent walking the prototype chain
 }