[iOS] Enable SegmentationPlatformTipsEphemeralCard feature by default

Impact:
- Enables tip cards showing users how to use Lens and Enhanced Safe Browsing features
- Removes the experimental field trial configuration now that the feature is enabled by default

Technical implementation:
- Flips the feature flag for SegmentationPlatformTipsEphemeralCard from FEATURE_DISABLED_BY_DEFAULT to FEATURE_ENABLED_BY_DEFAULT
- Updates TipsEphemeralCardExperimentTrainParam to include only Lens and Enhanced Safe Browsing modules
- Removes the PriceTrackingPromoIOS field trial configuration as it's no longer needed

Testing:
- Unit tests have been updated in the parent CL to support this feature

Fixed: 403620387
Change-Id: I4c27fb5fcdf7478f18886cbd8502dfe8b55a9a6f
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/6361654
Reviewed-by: Sylvain Defresne <sdefresne@chromium.org>
Commit-Queue: Benjamin Williams <bwwilliams@google.com>
Cr-Commit-Position: refs/heads/main@{#1433542}