(Linux only) No longer necessary to git clone the submodules

[SlySven]

In installers/generic-linux/build-and-make-installer.sh on line 20:

git clone --recursive https://github.com/Mudlet/Mudlet.git source

no longer needs to be recursive to pull in all the submodules as that is now handled in the CMake/QMake project files which only pull in the sub-modules needed for each platform.

I believe the line should be changed to:

git clone https://github.com/Mudlet/Mudlet.git source