fix(launch): remove deadsnakes from accelerator build step

[bcsherma]

Description

• Fixes WB-16937

This PR removes 3 commands from the accelerator build step. The first two steps add nvidia repos for installing cuda, but these are never used since we assume the base image has the accelerator libraries. The last step adds the deadsnakes ppa, which is a community library that enables installing specific patch versions (e.g. 3.9.12) of python. But the code also already resolves to a minor version (e.g. 3.9) which just works without the extra ppa.

The problem in the linked ticket was caused by the use of the add-apt-repository command, which is an extension of apt that is not widely compatible with debian container images.

Testing

How was this PR tested?

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Comparison is base (3f0150a) 79.68% compared to head (ccd3fe8) 76.95%.

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #6933      +/-   ##
==========================================
- Coverage   79.68%   76.95%   -2.74%     
==========================================
  Files         462      462              
  Lines       52747    52747              
==========================================
- Hits        42033    40593    -1440     
- Misses      10416    11848    +1432     
- Partials      298      306       +8     

Flag	Coverage Δ
func	48.51% <ø> (-0.19%)	⬇️
system	60.67% <ø> (-1.34%)	⬇️
unit	56.22% <ø> (-3.15%)	⬇️

Flags with carried forward coverage won't be shown. Click here to find out more.

Files	Coverage Δ
wandb/sdk/launch/builder/build.py	85.28% <ø> (ø)

... and 61 files with indirect coverage changes