Ensure scons source isn't obfuscated by liblouis test tables target (#16537)
Fixes #16535
Fixup of #16208
Summary of the issue:
#16208 introduced test tables SCons didn't want to copy to the test directory by default. I tried to fix that by binding testTable to the source target with env.Alias, but that's definitely the wrong way.
Description of user facing changes
Fixed build system.
Description of development approach
Added the test tables as a dependency to the liblouis python wrapper. This ensures that test tables will be there when the python wrapper is build.