Rename qml.Interferometer to qml.InterferometerUnitary

[AkashNarayanan]

Context:
This PR renames qml.Interferometer to qml.InterferometerUnitary in order to distinguish it from qml.templates.Interferometer.

Description of the Change:

• Renamed qml.Interferometer to qml.InterferometerUnitary and updated references to it throughout the code base.
• Removed the deprecation warning regarding the renaming of the operation.
• Updated the test cases.

Rendered Documentation Page:
qml.InterferometerUnitary

Benefits:

• Improves the distinction between the operation and the template.
• qml.templates.Interferometer can now be turned into an operation since the name conflict has been resolved.

Related GitHub Issues:
#1709

[codecov]

Codecov Report

Merging #1714 (51454f3) into master (05b1987) will decrease coverage by 0.00%.
The diff coverage is 100.00%.

@@            Coverage Diff             @@
##           master    #1714      +/-   ##
==========================================
- Coverage   99.21%   99.21%   -0.01%     
==========================================
  Files         204      204              
  Lines       15429    15425       -4     
==========================================
- Hits        15308    15304       -4     
  Misses        121      121              

Impacted Files	Coverage Δ
...ennylane/circuit_drawer/representation_resolver.py	99.36% <ø> (ø)
pennylane/devices/default_gaussian.py	99.64% <100.00%> (ø)
pennylane/ops/cv.py	100.00% <100.00%> (ø)

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[AkashNarayanan]

Hi @antalszava ! Can I implement this change too?

In addition to the PennyLane code base, the change should also be implemented with a separate PR in the StrawberryFields plugin that is not part of this repo, but in here.

[AkashNarayanan]

I am not sure why codecov/project is failing. It states here as follows

Everything is accounted for!
No changes detected that need to be reviewed.

[rmoyard]

Hey @AkashNarayanan, I will check your PR as soon as possible. Thank you for your contribution!

[rmoyard]

Hi @AkashNarayanan, thank you for the great contribution! It looks good to me but I don't know why the coverage is failing. I'll come back to you later.

[rmoyard]

Hi @antalszava ! Can I implement this change too?

In addition to the PennyLane code base, the change should also be implemented with a separate PR in the StrawberryFields plugin that is not part of this repo, but in here.

Yes for sure you can go for it, it should be straightforward!

[rmoyard]

It looks good to me, @josh146 you can bypass codecov and merge it 💯