misc(proj): Drop armv7 ARCHS

CI generated errors because of it.

```
❌  error: The armv7 architecture is deprecated. You should update your ARCHS build setting to remove the armv7 architecture. (in target 'MumbleKit (iOS)' from project 'MumbleKit')
```

Is this the place to drop it? Is this sufficient or does it also need submodule 3rdparty/** updates?

cfg/Base.xcconfig

@@ -2,7 +2,7 @@
 // Use of this source code is governed by a BSD-style
 // license that can be found in the LICENSE file.
 
-ARCHS = armv7 armv7s arm64
+ARCHS = arm64
 SDKROOT = iphoneos
 
 MACOSX_DEPLOYMENT_TARGET = 10.7