Remove call for action from WM enhancement issue template

i3 feature set is mostly frozen as well, so we shouldn't advise people
to open feature requests there. Moreover, i3 will disregard feature
requests from sway users (because it doesn't benefit the i3 project
itself).

There is now no good way to request new WM features, and this is by
design. This aligns with [1].

[1]: fc1148da7f

.github/ISSUE_TEMPLATE/enhancement.md

@@ -6,7 +6,7 @@ labels: 'enhancement'
 ---
 
 ### Please read the following before submitting:
-- We are not accepting any new window management features unless they get implemented by i3. Please consider searching for or opening an i3 feature request.
+- We are not accepting any new window management features unless they get implemented by i3.
 
 ### Please fill out the following:
 - **Description:**