[9.18] rem: usr: Remove ineffective TCP fallback after repeated UDP timeouts

When an authoritative server failed to respond to two consecutive
UDP queries, named marked the next retry as TCP but still sent it
over UDP, producing misleading dnstap records. The ineffective
retry path has been removed; a corrected TCP fallback will be
restored in future BIND 9 versions.

Closes #5529

Backport of MR !12022

Merge branch 'backport-5529-fix-tcp-fallback-after-udp-timeouts-9.18' into 'bind-9.18'

See merge request isc-projects/bind9!12050