Change references of pennylane master to main

[runora95]

Context:
Pennylane changed its default branch from master to main. Some of the workflows in lightning have started to fail with their pennylane@master references.

Description of the Change:
Change all references of pennylane master to main.

Benefits:
Workflows and reference to pennylane will be updated.

Possible Drawbacks:
None

Related GitHub Issues:
N/A

[github-actions]

Hello. You may have forgotten to update the changelog!
Please edit .github/CHANGELOG.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.

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 94.76%. Comparing base (7118417) to head (fa80080).
⚠️ Report is 1 commits behind head on master.

Additional details and impacted files

@@            Coverage Diff             @@
##           master    #1351      +/-   ##
==========================================
+ Coverage   93.47%   94.76%   +1.29%     
==========================================
  Files         187      187              
  Lines       29581    29581              
==========================================
+ Hits        27650    28032     +382     
+ Misses       1931     1549     -382     

Flag	Coverage Δ
unit_tests	94.76% <100.00%> (+1.29%)	⬆️

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[maliasadi]

Thanks for the quick fix @runora95!

Please add a changelog entry and check the Lightning CIs + PTM before merging the PR.

[josephleekl]

I've triggered a stable/stable and latest/latest PTM workflow to check everything goes well

[josephleekl]

@runora95 i see you've made some updates - would you mind triggering these with your branch to make sure they work?
https://github.com/PennyLaneAI/pennylane-lightning/actions/workflows/compat-check-stable-stable.yml
https://github.com/PennyLaneAI/pennylane-lightning/actions/workflows/compat-check-latest-latest.yml
https://github.com/PennyLaneAI/pennylane-lightning/actions/workflows/compat-docker-stable.yml
https://github.com/PennyLaneAI/pennylane-lightning/actions/workflows/compat-docker-latest.yml

[josephleekl]

Thanks @runora95 !