chore: remove temp fix for optional params support

[twishabansal]

We're currently not using optional parameters in Toolbox, as they create compatibility problems with LlamaIndex agents that utilize the AgentWorkflow class.

Using AgentWorkflow with Optional Parameters support would need some workarounds which will be investigated upon the addition of the Optional Parameters functionality.

The current implementation of each tool contains tool properties with tool types being any of String or Null.

'param1': {'anyOf': [{'type': 'string'}, {'type': 'null'}], 'description': ..., 'title': ...}

The Agent Workflow needs params to have a single type like:

 'param1': {'type': 'string', 'description': ..., 'title': ...}

[anubhav756]

To avoid redundancy, could you clarify if this change is related to googleapis/mcp-toolbox-sdk-python#68? If they are related, we may be able to eliminate additional code, as done in that PR.

[twishabansal]

To avoid redundancy, could you clarify if this change is related to googleapis/genai-toolbox-langchain-python#68? If they are related, we may be able to eliminate additional code, as done in that PR.

This issue was discovered while trying to use LlamaIndex AgentWorkflow to develop a LlamaIndex Quickstart.

While the method of discovery was different, these two PRs essentially achieve the same goal functionality. Will remove some other redundant code based on googleapis/genai-toolbox-langchain-python#68. Thanks for pointing this out @anubhav756 !