Update the forum link on the main page

[David_Hedlund]

On https://f-droid.org/wiki/page/Main_Page, change:

or post in the [Forums – F-Droid forums].

to

or post in the [https://forum.f-droid.org/ forum].

[mimi89999]

@David_Hedlund Corrected. Thanks.

[David_Hedlund]

Thank you for helping out.