fix(apple): Simplify app start tracing (#15109)

Remove the section on before Cocoa SDK v 8.18.0, which we released in
Jan 2024, to simplify the app start tracing docs.

Author: philipphofmann

docs/platforms/apple/common/tracing/instrumentation/automatic-instrumentation.mdx

@@ -110,8 +110,7 @@ Sentry's App Start instrumentation aims to be as comprehensive and representativ
 For example, Sentry measures the duration from process start, including the time before before runtime initialization and before the first application object is loaded, until the first frame is rendered to the user.
 
 </Alert>
-
-Since [sentry-cocoa 8.18.0](https://github.com/getsentry/sentry-cocoa/releases/tag/8.18.0) the SDK creates the following app start spans:
+The Cocoa SDK creates the following app start spans:
 
 - **Pre Runtime Init**: from the process start time to the runtime init.
 - **Runtime Init to Pre Main Initializers**: from runtime init to pre main initializers.
@@ -121,13 +120,6 @@ Since [sentry-cocoa 8.18.0](https://github.com/getsentry/sentry-cocoa/releases/t
 
 ![App Start Transaction](./img/app-start-transaction.png)
 
-Before [sentry-cocoa 8.18.0](https://github.com/getsentry/sentry-cocoa/releases/tag/8.18.0) the SDK creates the following app start spans:
-
-- **Pre Runtime Init**: from the process start time to the runtime init.
-- **Runtime Init to Pre Main Initializers**: from runtime init to pre main initializers.
-- **UIKit and Application Init**: from pre main initializers to [`didFinishLaunchingNotification`][didfinishlaunching].
-- **Initial Frame Render**: from the [`didFinishLaunchingNotification`][didfinishlaunching] to [`UIWindowDidBecomeVisibleNotification`][uiwindow].
-
 Cold and warm start are Mobile Vitals, which you can learn about in the [full documentation](/product/insights/mobile/mobile-vitals).
 
 ### Prewarmed App Start Tracing