lighttpd: drop hard-coded lua version in PACKAGECONFIG

lighttpd: drop hard-coded lua version in PACKAGECONFIG

When building lighttpd with PACKAGECONFIG_append_pn-lighttpd = "lua" in local.conf,
bitbake gives the following error:

ERROR: Nothing PROVIDES 'lua5.1' (but /home/tgamblin/build/oe-core/meta/recipes-extended/lighttpd/lighttpd_1.4.54.bb DEPENDS on or otherwise requires it)
NOTE: Runtime target 'lighttpd' is unbuildable, removing...
Missing or unbuildable dependency chain was: ['lighttpd', 'lua5.1']

Removing the "5.1" from the PACKAGECONFIG line in lighttpd_1.4.54.bb fixes the issue.

Signed-off-by: Trevor Gamblin <trevor.gamblin@windriver.com>
Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>