Remove PowerPC wheels for LQ

[maliasadi]

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---

Context:
Remove PowerPC wheel recipe for Lightning-Qubit. Users can still install LQ from source by following the installation guideline:

pip install pennylane-lightning --no-binary :all:

Description of the Change:

• Remove .github/workflows/wheel_linux_ppc64le.yml
• Update README

Benefits:
Reduce the number of wheels recipes and CI checks per PR. We can revert this if it turns out that many rely on these wheels.

Possible Drawbacks:
PowerPC wheels will not be built and uploaded to PyPI and TestPyPI starting with v0.39.0

Related GitHub Issues:
[sc-73503]

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 59.06%. Comparing base (75dfecb) to head (1ffbc13).
Report is 75 commits behind head on master.

❗ There is a different number of reports uploaded between BASE (75dfecb) and HEAD (1ffbc13). Click for more details.

HEAD has 34 uploads less than BASE

Flag	BASE (75dfecb)	HEAD (1ffbc13)
	40	6

Additional details and impacted files

@@             Coverage Diff             @@
##           master     #902       +/-   ##
===========================================
- Coverage   97.67%   59.06%   -38.62%     
===========================================
  Files         212       24      -188     
  Lines       29084     2162    -26922     
===========================================
- Hits        28408     1277    -27131     
- Misses        676      885      +209     

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[vincentmr]

LGTM, thanks @maliasadi .

[mlxd]

So long, PPC64LE.

[AmintorDusko]