[gdb/testsuite] Fix gdb.tui/wrap-line.exp

PR testsuite/30458 reports the following FAIL:
...
PASS: gdb.tui/wrap-line.exp: width-auto-detected: cli: wrap
^CQuit
(gdb) WARNING: timeout in accept_gdb_output
Screen Dump (size 50 columns x 24 rows, cursor at column 6, row 3):
    0 Quit
    1 (gdb) 7890123456789012345678901234567890123456789
    2 W^CQuit
    3 (gdb)
  ...
FAIL: gdb.tui/wrap-line.exp: width-auto-detected: cli: prompt after wrap
...

The problem is that the regexp doesn't account for the ^C:
...
    gdb_assert { [Term::wait_for "^WQuit"] } "prompt after wrap"
...

The ^C occurs occasionally.  This is something we'd like to fix.  It's
reported as a readline problem here (
https://lists.gnu.org/archive/html/bug-readline/2023-06/msg00000.html ).

For now, fix this by updating the regexp, and likewise in another place in the
test-case where we use ^C.

Tested on x86_64-linux.

Bug: https://sourceware.org/bugzilla/show_bug.cgi?id=30458