Fix tests and note that deprecated constants are not exported

Since nodejs/node#49686, they are not
enumerable properties, so Object.assign doesn't re-export them.
Attempting to directly export them would trigger the deprecation
warning.

Author: RyanZim

README.md

@@ -57,6 +57,8 @@ const fs = require('fs')
 const fse = require('fs-extra')
 ```
 
+**NOTE:** The deprecated constants `fs.F_OK`, `fs.R_OK`, `fs.W_OK`, & `fs.X_OK` are not exported on Node.js v24.0.0+; please use their `fs.constants` equivalents. 
+
 ### ESM
 
 There is also an `fs-extra/esm` import, that supports both default and named exports. However, note that `fs` methods are not included in `fs-extra/esm`; you still need to import `fs` and/or `fs/promises` seperately:

lib/fs/__tests__/fs-integration.test.js

@@ -27,6 +27,5 @@ describe('native fs', () => {
 
   it('should have native fs constants', () => {
     assert.strictEqual(fse.constants.F_OK, fs.constants.F_OK)
-    assert.strictEqual(fse.F_OK, fs.F_OK) // soft deprecated usage, but still available
   })
 })