Remove X and P

[lillian542]

Removes CV observables qml.X and qml.P (deprecated last release in favour of qml.QuadX and qml.QuadP)

[github-actions]

Hello. You may have forgotten to update the changelog!
Please edit doc/releases/changelog-dev.md with:

• A one-to-two sentence description of the change. You may include a small working example for new features.
• A link back to this PR.
• Your name (or GitHub username) in the contributors section.

[lillian542]

[sc-43898]

[codecov]

Codecov Report

Merging #4533 (c64b88e) into master (2468bcb) will decrease coverage by 0.01%.
Report is 1 commits behind head on master.
The diff coverage is 100.00%.

@@            Coverage Diff             @@
##           master    #4533      +/-   ##
==========================================
- Coverage   99.66%   99.66%   -0.01%     
==========================================
  Files         376      376              
  Lines       33074    33061      -13     
==========================================
- Hits        32964    32951      -13     
  Misses        110      110              

Files Changed	Coverage Δ
pennylane/data/attributes/operator/operator.py	100.00% <ø> (ø)
pennylane/gradients/parameter_shift_cv.py	99.61% <ø> (ø)
pennylane/ops/cv.py	100.00% <ø> (ø)
pennylane/tape/__init__.py	100.00% <ø> (ø)
pennylane/tape/qscript.py	100.00% <ø> (ø)
pennylane/devices/default_gaussian.py	100.00% <100.00%> (ø)

[albi3ro]

🚀

[mudit2812]

Thanks! Here's a 🚀