fix: harmonise "SIM swap" casing and subscriptionId examples (fixes #308)

[albertoramosmonagas]

What type of PR is this?

Add one of the following kinds:

• correction

What this PR does / why we need it:

What type of PR is this?

correction

What this PR does / why we need it:

Addresses the two leftovers from the Release Management review of the r4.2 rc snapshot, after #305 fixed #288 for titles, tags, operation summaries and subscription operation examples:

1. Replaces the remaining lowercase "sim swap" / "Sim Swap" with "SIM swap" in descriptions and test definitions (sim-swap.yaml, sim-swap-subscriptions.yaml, sim-swap-subscriptions.feature).
2. Aligns subscriptionId in the SWAPPED and SUBSCRIPTION_ENDS notification examples with the subscription id used in the subscription examples (550e8400-e29b-41d4-a716-446655440000).

Which issue(s) this PR fixes:

Fixes #308

Special notes for reviewers:

• Only descriptions, comments and example values change. There is no change to the API behaviour or schemas.
• "sim card" / "sim's" in lowercase remain in the .feature files. That is a different term from "SIM swap", so I left it out of scope. Happy to include it if preferred.

Changelog input

 release-note
Harmonise "SIM swap" casing in descriptions and test definitions, and align the subscriptionId in the notification examples with the subscription examples.

[bigludo7]

LGTM