[ios] Podspec bump to v4.8.0 alpha.1 (#13696)

* [ios, macos] Podspec bump to 4.8.0-alpha.1.

* [ios] Update changelogs.

platform/ios/CHANGELOG.md

@@ -2,7 +2,7 @@
 
 Mapbox welcomes participation and contributions from everyone. Please read [CONTRIBUTING.md](../../CONTRIBUTING.md) to get started.
 
-## master
+## 4.8.0
 
 * Added an `MGLStyle.performsPlacementTransitions` property to control how long it takes for colliding labels to fade out. ([#13565](https://github.com/mapbox/mapbox-gl-native/pull/13565))
 * Fixed a crash when casting large numbers in `NSExpression`. ([#13580](https://github.com/mapbox/mapbox-gl-native/pull/13580))

platform/ios/Mapbox-iOS-SDK-nightly-dynamic.podspec

@@ -1,6 +1,6 @@
 Pod::Spec.new do |m|
 
-  version = '4.7.0'
+  version = '4.8.0-alpha.1'
 
   m.name    = 'Mapbox-iOS-SDK-nightly-dynamic'
   m.version = "#{version}-nightly"

platform/ios/Mapbox-iOS-SDK-stripped.podspec

@@ -1,6 +1,6 @@
 Pod::Spec.new do |m|
 
-  version = '4.7.0'
+  version = '4.8.0-alpha.1'
 
   m.name    = 'Mapbox-iOS-SDK-stripped'
   m.version = "#{version}-stripped"

platform/ios/Mapbox-iOS-SDK.podspec

@@ -1,6 +1,6 @@
 Pod::Spec.new do |m|
 
-  version = '4.7.0'
+  version = '4.8.0-alpha.1'
 
   m.name    = 'Mapbox-iOS-SDK'
   m.version = version