devel/hs-ghcup: Update to 0.2.6.2

ChangeLog:

• https://github.com/haskell/ghcup-hs/releases/tag/v0.2.6.2
• https://github.com/haskell/ghcup-hs/releases/tag/v0.2.6.1
• https://github.com/haskell/ghcup-hs/releases/tag/v0.2.6.0

MFH: 2026Q2
Differential Revision: https://reviews.freebsd.org/D57560