[AC-2001] EXE file is able to upload while composing mail

Steps to reproduce: 1) Launch browser. 2) Enter Gmail url from the browser and click on enter button from the key board. 3) Login screen is loaded. 4) Enter valid user name and password Username: gateway Password:gateway111 Click on "Sign in" button 5) User home page is loaded. 6) Click on "Compose" button, Compose window is opened. 7) Enter email address form the "To" address field. 8) Click on "Attach files" link button, Path window is opened. 9) Select .EXE file (Example: a.exe) Expected Value: Should throw an appropriate alert message i.e. "EXE files are not allowed" Actual Value: Error message is not displayed and EXE file is uploaded.