Update pgvector dependency to version 0.3.6

[iamarunbrahma]

Description

Updates the pgvector dependency from ^0.2.4 to ^0.3.6 in the llama-index-vector-stores-postgres package. This update ensures compatibility with newer versions of pgvector and resolves dependency issues reported in #17166.

Fixes #17166

New Package?

Did I fill in the tool.llamahub section in the pyproject.toml and provide a detailed README.md for my new integration or package?

• Yes
• No (Not applicable - this is an update to an existing package)

Version Bump?

Did I bump the version in the pyproject.toml file of the package I am updating? (Except for the llama-index-core package)

• Yes
• No (Version bump not required for dependency update only)

Type of Change

• Bug fix (non-breaking change which fixes an issue)
• New feature (non-breaking change which adds functionality)
• Breaking change (fix or feature that would cause existing functionality to not work as expected)
• This change requires a documentation update

How Has This Been Tested?

• I believe this change is already covered by existing unit tests
  • The existing Postgres vector store tests in tests/test_vector_stores_postgres.py cover the functionality
  • The pgvector update is backward compatible and doesn't introduce breaking changes

Suggested Checklist:

• I have performed a self-review of my own code
• I have commented my code, particularly in hard-to-understand areas
• I have made corresponding changes to the documentation
• I have added Google Colab support for the newly added notebooks (Not applicable)
• My changes generate no new warnings
• I have added tests that prove my fix is effective or that my feature works
• New and existing unit tests pass locally with my changes
• I ran make format; make lint to appease the lint gods

[masci]

Thank you!