Fix typos in BasePassManager messages and docstrings

[ManuelEsparcia]

This PR fixes several small typos in qiskit.passmanager.BasePassManager:

• Error messages in replace() and remove() now say “does not exist” instead of “does not exists”.
• The append() and replace() docstrings now refer to “pass manager Task” instead of “passmanager Task”.
• The run() docstring now uses the grammatically correct phrase
  “The exact arguments passed expose the internals of the pass manager…”.

These changes are purely textual and do not affect runtime behavior.

[qiskit-bot]

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[coveralls]

Pull Request Test Coverage Report for Build 19834444145

Details

• 1 of 2 (50.0%) changed or added relevant lines in 1 file are covered.
• 7 unchanged lines in 2 files lost coverage.
• Overall coverage increased (+0.01%) to 88.395%

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Changes Missing Coverage	Covered Lines	Changed/Added Lines	%
qiskit/passmanager/passmanager.py	1	2	50.0%

Files with Coverage Reduction	New Missed Lines	%
crates/circuit/src/parameter/parameter_expression.rs	1	82.3%
crates/qasm2/src/lex.rs	6	91.77%

Totals
Change from base Build 19833347399:	0.01%
Covered Lines:	95744
Relevant Lines:	108314

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💛 - Coveralls

[jakelishman]

Please can you review all of the PRs you've opened, and ensure that each PR contains only the changes it's intended to, and isn't built on top of unrelated PRs.

[ManuelEsparcia]

I’ve cleaned up this PR so it only contains the minimal typo fixes in BasePassManager, changing “passmanager Task” to “pass manager Task” in the docstrings and “does not exists” to “does not exist” in the error messages (two occurrences), with no other files or changes included now.