Update authorizing-oauth-apps.md

I found that this request should be GET instead of POST, so I made this change

Author: lopo12123

content/apps/oauth-apps/building-oauth-apps/authorizing-oauth-apps.md

@@ -79,7 +79,7 @@ If the user accepts your request, {% data variables.product.github %} redirects
 
 Exchange this `code` for an access token:
 
-    POST {% data variables.product.oauth_host_code %}/login/oauth/access_token
+    GET {% data variables.product.oauth_host_code %}/login/oauth/access_token
 
 This endpoint takes the following input parameters.