Do a shallow git fetch instead of full fetch

[codekansas]

Doing a shallow git fetch is a lot faster and lets the script run much more quickly without affecting the script's behavior

[Nir-Az]

@codekansas Thanks for your contribution,
For future contributions please align to our contribution guide and base & target the changes to development branch

@dmipx looks like a nice optimization right?

Can be also updated in our kernel 5.13/5.15 script

[codekansas]

Yeah, I was just following the install instructions and found this change made it go a lot faster, and I thought it'd be immediately useful for other people. It's a pretty minimal change so I just figured I'd throw it over the wall (I think there's other scripts which also fetch the entire Ubutu repo that would benefit but I wasn't trying them out). I'll be sure to use the development branch if I do end up making deeper changes later

[dmipx]

LGTM
Good catch!
@Nir-Az please change this PR to development branch.
@codekansas Can you add same change to the following script (new kernels support): https://github.com/IntelRealSense/librealsense/blob/development/scripts/patch-realsense-ubuntu-lts-hwe.sh ?
This PR will be merged to both scripts.

[codekansas]

Closing this PR in favor of the other one (which is based off my fork's development branch): #11041