Revert "package/prosody: use correct bit32 package"

Revert "package/prosody: use correct bit32 package"

This reverts commit fa84c176c2148a60103e850204180f86aa5baa73 that
replace luabitop by lua_bit32 package when lua 5.1 is used.

Since this change the prosody test in gitlab is fail due to
missing lua-bitops [1]:

Starting prosody:
**************************
Prosody was unable to find lua-bitops
This package can be obtained in the following ways:

    Source:           http://bitop.luajit.org/
    Debian/Ubuntu:    sudo apt-get install lua-bitop
    luarocks:         luarocks install luabitop

WebSocket support will not be available
More help can be found on our website, at https://prosody.im/doc/depends
**************************

The upstream documentation [2] is misleading (or not uptodate)
about lua-bit32 dependency.

Since bitop is builtin since lua5.2, we probably need to select
luabitop package only when lua 5.1 is used as lua interpreter.

Tested with run-tests:
./support/testing/run-tests tests.package.test_prosody.TestProsodyLua51

[1] https://gitlab.com/buildroot.org/buildroot/-/jobs/576271975
[2] https://prosody.im/doc/depends#bitop

Signed-off-by: Romain Naour <romain.naour@gmail.com>
Cc: James Hilliard <james.hilliard1@gmail.com>
Cc: Yann E. MORIN <yann.morin.1998@free.fr>
Signed-off-by: Thomas Petazzoni <thomas.petazzoni@bootlin.com>