include: fib: Remove the deprecated UID fields

This change removes the deprecated fields FRA_UID_START and FRA_UID_END.
These fields should have been removed as part of
commit 9789b697c6e4db7 ("Revert "net: core: Support UID-based routing."")
but they were incorrectly resolved as part of the merge commit.

CRs-Fixed: 2079190
Change-Id: Id7981ce8c22bc27d8d39d9ac59e2b1e1a80b8cfe
Signed-off-by: Subash Abhinov Kasiviswanathan <subashab@codeaurora.org>