[gdb/testsuite] Fix license text in gdb.reverse/map-to-same-line.{c,exp}

I noticed in gdb.reverse/map-to-same-line.{c,exp} that the license urls are
using some kind of indirection via urldefense.proofpoint.com.

Fix this by removing this indirection.

Tested on x86_64-linux.

PR testsuite/31358
Bug: https://sourceware.org/bugzilla/show_bug.cgi?id=31358