Fixed type in documentation Common Coding Mistakes

Author: msutovsky-r7

docs/metasploit-framework.wiki/Common-Metasploit-Module-Coding-Mistakes.md

@@ -146,7 +146,7 @@ register_options(
   ], self.class)
 ```
 
-**8. Neglecting to use send_request_cgi()'s vars_get or vars_get when crafting a POST/GET request**
+**8. Neglecting to use send_request_cgi()'s vars_post or vars_get when crafting a POST/GET request**
 
 ```ruby
 data_post = 'user=jsmith&pass=hello123'
@@ -199,4 +199,4 @@ Metasploit3.new
 ```ruby
 # https://github.com/rapid7/metasploit-framework/issues/3853
 datastore['BAD'] = 'This is bad.'
-```
+```