lua: Remove lua5.1

* we have lua-5.2 in "lua" recipe and lua-5.1 in "lua5.1", but these
  aren't completely separate in sysroot:
  WARNING: The recipe lua is trying to install files into a shared area when those files already exist. Those files and their manifest location are:
   /OE/build/oe-core/tmp-eglibc/sysroots/qemux86/usr/include/lauxlib.h
   Matched in manifest-qemux86-lua5.1.populate_sysroot
   /OE/build/oe-core/tmp-eglibc/sysroots/qemux86/usr/include/lua.h
   Matched in manifest-qemux86-lua5.1.populate_sysroot
   /OE/build/oe-core/tmp-eglibc/sysroots/qemux86/usr/include/lua.hpp
   Matched in manifest-qemux86-lua5.1.populate_sysroot
   /OE/build/oe-core/tmp-eglibc/sysroots/qemux86/usr/include/luaconf.h
   Matched in manifest-qemux86-lua5.1.populate_sysroot
   /OE/build/oe-core/tmp-eglibc/sysroots/qemux86/usr/include/lualib.h
   Matched in manifest-qemux86-lua5.1.populate_sysroot
   /OE/build/oe-core/tmp-eglibc/sysroots/qemux86/usr/lib/liblua.a
   Matched in manifest-qemux86-lua5.1.populate_sysroot
  Please verify which package should provide the above files.
  Causing some undeterministic behavior.
* keep only 5.2 in "lua"

Signed-off-by: Martin Jansa <Martin.Jansa@gmail.com>