Update tests due to the deprecated qml.sample usage when shots=None

[antalszava]

Some test cases needed adjustment due to: PennyLaneAI/pennylane#1522.

Note: since only the test cases are updated, there is no need to incorporate the changes in the release candidate branch. Having them in master will help with passing the checks in the plugin test matrix.

[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

Merging #132 (b0ea028) into master (333ed09) will not change coverage.
The diff coverage is n/a.

@@            Coverage Diff            @@
##            master      #132   +/-   ##
=========================================
  Coverage   100.00%   100.00%           
=========================================
  Files            3         3           
  Lines           71        71           
=========================================
  Hits            71        71           

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[github-actions]

Test Report (C++) on Ubuntu

    1 files  ±0      1 suites  ±0   0s ⏱️ ±0s
164 tests ±0  164 ✔️ ±0  0 💤 ±0  0 ❌ ±0 
694 runs  ±0  694 ✔️ ±0  0 💤 ±0  0 ❌ ±0 

Results for commit 864ea2c. ± Comparison against base commit 864ea2c.

♻️ This comment has been updated with latest results.

[albi3ro]

seems all good.