Update giffgaff to "Yes" for eSIM

[secretwolfie]

giffgaff recently rolled out eSIM Support after succeeding with installing IMS; A system that's funamental to VoLTE, Visual Voicemail deployment, seems like we're heading in the right direction.

Here's giffgaff's official eSIM support page: https://www.giffgaff.com/blog/giffgaff-news/how-to-get-a-giffgaff-esim/