chore: fix grammer

Author: fahimfaisaal

Ciphers/test/Atbash.test.js

@@ -1,7 +1,7 @@
 import Atbash from '../Atbash'
 
 describe('Testing Atbash function', () => {
-  it('Test - 1, passing the non-string as an argument', () => {
+  it('Test - 1, passing a non-string as an argument', () => {
     expect(() => Atbash(0x345)).toThrow()
     expect(() => Atbash(123)).toThrow()
     expect(() => Atbash(123n)).toThrow()