Remove support for changing magnification of active pane (#31981)

Closes #4265
Closes #24600

This setting causes many visual defects, and introduces unnecessary
(maintenance) complexity. as seen by #4265 and #24600


CC: @iamnbutler - How do you feel about this? I recommend looking at
https://github.com/zed-industries/zed/pull/24150#issuecomment-2866706506
for more context

Release Notes:

- Removed support

---------

Co-authored-by: Peter <peter@zed.dev>

docs/src/configuring-zed.md

@@ -38,23 +38,12 @@ Extensions that provide language servers may also provide default settings for t
 ```json
 {
   "active_pane_modifiers": {
-    "magnification": 1.0,
     "border_size": 0.0,
     "inactive_opacity": 1.0
   }
 }
 ```
 
-### Magnification
-
-- Description: Scale by which to zoom the active pane. When set to `1.0`, the active pane has the same size as others, but when set to a larger value, the active pane takes up more space.
-- Setting: `magnification`
-- Default: `1.0`
-
-**Options**
-
-`float` values
-
 ### Border size
 
 - Description: Size of the border surrounding the active pane. When set to 0, the active pane doesn't have any border. The border is drawn inset.

docs/src/fonts.md

@@ -31,8 +31,6 @@ TBD: Explain various font settings in Zed.
   - `terminal.font-size`
   - `terminal.font-family`
   - `terminal.font-features`
-- Other settings:
-  - `active-pane-magnification`
 
 ## Old Zed Fonts