docs: Fix environment variables names

[diegolovison]

Description of your changes:
Fix environment variable names

The current code is using os.environ['my-secret'] but we are setting the environment variable to be SECRET_VAR

    kubernetes.use_secret_as_env(task,
                                 secret_name='my-secret',
                                 secret_key_to_env={'password': 'SECRET_VAR'})

The code os.environ['my-secret'] will return an error

print(os.environ['my-secret'])
File "/usr/lib64/python3.9/os.py", line 679, in __getitem__
raise KeyError(key) from None
KeyError: 'my-secret'

The goal of this PR is to fix the doc issue.

Checklist:

• [ X ] The title for your pull request (PR) should follow our title convention. Learn more about the pull request title convention used in this repository.

[google-oss-prow]

@diegolovison: The following test failed, say /retest to rerun all failed tests or /retest-required to rerun all mandatory failed tests:

Test name	Commit	Details	Required	Rerun command
kfp-kubernetes-execution-tests	2254d93	link	false	/test kfp-kubernetes-execution-tests

Instructions for interacting with me using PR comments are available here. If you have questions or suggestions related to my behavior, please file an issue against the kubernetes-sigs/prow repository. I understand the commands that are listed here.

[DharmitD]

Tested this out by creating a pipeline and a run using a yaml created out of the previous example snippet. Observed this error on run creation:

File "/tmp/tmp.j8rF6VFIdK/ephemeral_component.py", line 9, in print_secret
print(os.environ['my-secret'])
File "/usr/lib64/python3.9/os.py", line 679, in __getitem__
raise KeyError(key) from None
KeyError: 'my-secret'

Generated a yaml out of this fixed example snippet, created a pipeline and run. Run completed successfully.

[KFP Executor 2024-07-16 20:09:45,963 INFO]: Looking for component `print_secret` in --component_module_path `/tmp/tmp.Lz61ANvhsm/ephemeral_component.py`
[KFP Executor 2024-07-16 20:09:45,963 INFO]: Loading KFP component "print_secret" from /tmp/tmp.Lz61ANvhsm/ephemeral_component.py (directory "/tmp/tmp.Lz61ANvhsm" and module name "ephemeral_component")

/lgtm

[gregsheremeta]

/lgtm

[gregsheremeta]

forwarding to @chensun for final review and approval :)

[google-oss-prow]

[APPROVALNOTIFIER] This PR is APPROVED

This pull-request has been approved by: chensun

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[DharmitD]

@diegolovison could you please rebase? That should remove the failing Prow test and this PR shall get merged.

[hbelmiro]

/lgtm