REGTESTS: Remove REQUIRE_VERSION=1.5 from all tests

HAProxy 1.5 is EOL, thus this always matches.

1.6 / 1.7 were already removed in:
d8be0018fe85b5f815d59cdf1e0400274a99a9b1 (1.6)
1b095cac9468d0c3eeb157e9b1a2947487bd3c83 (1.7)
1 file changed