Documentation/git-send-email.txt: Mention less secure app access might need to enable.

Looks like Google changed Gmail security and now less secure app access
needs to be explicitly enabled if 2-factor authentication is not in
place, otherwise send-mail fails with:

  5.7.8 Username and Password not accepted. Learn more at
  5.7.8  https://support.google.com/mail/?p=BadCredentials v5sm13756502ede.13 - gsmtp

Signed-off-by: Vasyl Vavrychuk <[email protected]>
Signed-off-by: Junio C Hamano <[email protected]>

Author: vvavrychuk

Documentation/git-send-email.txt

@@ -494,7 +494,11 @@ edit ~/.gitconfig to specify your account settings:
 	smtpServerPort = 587
 ----
 
-If you have multifactor authentication setup on your gmail account, you will
+If you do not have multi-factor authentication set up on your Gmail account, you
+will need to allow less secure app access. Visit
+https://myaccount.google.com/lesssecureapps to enable it.
+
+If you have multi-factor authentication set up on your Gmail account, you will
 need to generate an app-specific password for use with 'git send-email'. Visit
 https://security.google.com/settings/security/apppasswords to create it.