Python: Remove planner-related code and samples. (#12417)

### Motivation and Context

Per deprecation method, removing planner-related code after June 1,
2025.

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### Description

- Removing planner-related code.
- Closes #12400

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### Contribution Checklist

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- [X] The code builds clean without any errors or warnings
- [X] The PR follows the [SK Contribution
Guidelines](https://github.com/microsoft/semantic-kernel/blob/main/CONTRIBUTING.md)
and the [pre-submission formatting
script](https://github.com/microsoft/semantic-kernel/blob/main/CONTRIBUTING.md#development-scripts)
raises no violations
- [X] All unit tests pass, and I have added new tests where possible
- [ ] I didn't break anyone 😄

Author: moonbox3

python/mypy.ini

@@ -20,11 +20,6 @@ ignore_errors = true
 # TODO (eavanvalkenburg): remove this
 # https://github.com/microsoft/semantic-kernel/issues/6463
 
-[mypy-semantic_kernel.planners.*]
-ignore_errors = true
-# TODO (eavanvalkenburg): remove this after future of planner is decided
-# https://github.com/microsoft/semantic-kernel/issues/6465
-
 [mypy-semantic_kernel.connectors.memory.astradb.*]
 ignore_errors = true
 

python/samples/learn_resources/README.md

@@ -43,5 +43,5 @@ To run the console application within Visual Studio Code, just hit `F5`.
 Otherwise the sample can be run via the command line:
 
 ```
-python.exe <absolute_path_to_sk_code>/python/samples/documentation_examples/planner.py
+python.exe <absolute_path_to_sk_code>/python/samples/learn_resources/plugin.py
 ```