remove: remove lowercaseKeys from namespace

This commit removes the `lowercaseKeys` symbol from the `@stdlib/utils`
namespace due to a package migration.

BREAKING CHANGE: remove `lowercaseKeys`

To migrate, users should access the same symbol via the
`@stdlib/object` namespace.

Ref: #8755

Author: Neerajpathak07

lib/node_modules/@stdlib/utils/docs/types/index.d.ts

@@ -124,7 +124,6 @@ import keyBy = require( '@stdlib/utils/key-by' );
 import keyByRight = require( '@stdlib/utils/key-by-right' );
 import objectKeys = require( '@stdlib/utils/keys' );
 import keysIn = require( '@stdlib/utils/keys-in' );
-import lowercaseKeys = require( '@stdlib/utils/lowercase-keys' );
 import map = require( '@stdlib/utils/map' );
 import mapArguments = require( '@stdlib/utils/map-arguments' );
 import mapFun = require( '@stdlib/utils/map-function' );
@@ -3122,28 +3121,6 @@ interface Namespace {
 	*/
 	keysIn: typeof keysIn;
 
-	/**
-	* Converts each object key to lowercase.
-	*
-	* ## Notes
-	*
-	* -   The function only transforms own properties. Hence, the function does not transform inherited properties.
-	* -   The function shallow copies key values.
-	*
-	* @param obj - source object
-	* @returns new object
-	*
-	* @example
-	* var obj1 = {
-	*     'A': 1,
-	*     'B': 2
-	* };
-	*
-	* var obj2 = ns.lowercaseKeys( obj1 );
-	* // returns { 'a': 1, 'b': 2 }
-	*/
-	lowercaseKeys: typeof lowercaseKeys;
-
 	/**
 	* Applies a function to each element in an array and assigns the result to an element in a new array.
 	*

lib/node_modules/@stdlib/utils/lib/index.js

@@ -976,15 +976,6 @@ setReadOnly( utils, 'objectKeys', require( '@stdlib/utils/keys' ) );
 */
 setReadOnly( utils, 'keysIn', require( '@stdlib/utils/keys-in' ) );
 
-/**
-* @name lowercaseKeys
-* @memberof utils
-* @readonly
-* @type {Function}
-* @see {@link module:@stdlib/utils/lowercase-keys}
-*/
-setReadOnly( utils, 'lowercaseKeys', require( '@stdlib/utils/lowercase-keys' ) );
-
 /**
 * @name map
 * @memberof utils