docs(ios): correct iOS autocapture defaults

[singhvishalkr]

Problem

Closes #16182.

The iOS autocapture section of /docs/product-analytics/autocapture is wrong in two ways:

1. It says "Screen navigation autocapture is not enabled by default."
2. The Swift example comments config.captureApplicationLifecycleEvents = true as "Disabled by default."

Both contradict the posthog-ios SDK defaults:

@objc public var captureApplicationLifecycleEvents: Bool = true
@objc public var captureScreenViews: Bool = true

#if os(iOS) || targetEnvironment(macCatalyst)
    /// Default: false
    @objc public var captureElementInteractions: Bool = false
#endif

Changes

• Flip the sentence to say screen navigation autocapture is enabled by default.
• Add a Default column to the options table.
• Document the previously-missing captureElementInteractions option (iOS / Mac Catalyst only, default false).
• Rework the Swift example to show how to turn the defaults off while enabling element interactions, with accurate inline comments.

Preview

Before:

Screen navigation autocapture is not enabled by default. You can enable it by setting captureScreenViews to true in the config.

config.captureElementInteractions = true // Disabled by default
config.captureApplicationLifecycleEvents = true // Disabled by default

After:

Screen navigation autocapture is enabled by default. You can disable it by setting captureScreenViews to false in the config.

config.captureScreenViews = false                // Enabled by default
config.captureApplicationLifecycleEvents = false // Enabled by default
config.captureElementInteractions = true         // Disabled by default