Sanitize end of line character when loading token from a file (vault)

[mmenarguezpear]

This commit addresses #16406

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[boring-cyborg]

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[mmenarguezpear]

@mik-laj is there something else needed for a review?

[github-actions]

The PR is likely OK to be merged with just subset of tests for default Python and Database versions without running the full matrix of tests, because it does not modify the core of Airflow. If the committers decide that the full tests matrix is needed, they will add the label 'full tests needed'. Then you should rebase to the latest main or amend the last commit of the PR, and push it with --force-with-lease.

[mmenarguezpear]

I have also verified this change fixes the isse with the following Dockerfile

FROM apache/airflow:2.1.0-python3.8

COPY requirements.txt /opt/airflow/requirements.txt

RUN pip install -r /opt/airflow/requirements.txt

RUN sed -i s/\_client\.token\ =\ f\.read\(\)/\_client\.token\ =\ f\.read\(\)\.strip\(\)/g /home/airflow/.local/lib/python3.8/site-packages/airflow/providers/hashicorp/_internal_client/vault_client.py

COPY src /opt/airflow

where requirements.txt

apache-airflow-providers-amazon==1.4.0
apache-airflow==2.1.0
apache-airflow-providers-hashicorp==1.0.2

[boring-cyborg]

Awesome work, congrats on your first merged pull request!