Commit 1eb8556f5a ("gdb: add infrun_debug_printf macro") changed the
debug output format for `set debug infrun 1`. The test
gdb.threads/stepi-random-signal.exp uses that debug output, and was
updated, but not correctly. It results in this failure:
FAIL: gdb.threads/stepi-random-signal.exp: stepi (no random signal)
Fix it by adjusting the pattern in the test.
gdb/testsuite/ChangeLog:
PR gdb/26532
* gdb.threads/stepi-random-signal.exp: Update pattern.
Change-Id: If5fa525e9545e32a286effe6a6184358374bd37c