Update urllib3 to 2.6.3 to fix CVE-2026-21441

[mraible]

urllib3 2.6.1 and 2.6.2 contain a known security vulnerability (CVE-2026-21441) that is patched in version 2.6.3.

The current requirements.txt specifies urllib3>=2.6.1, which allows users to remain on the vulnerable version.

Request: Update the minimum requirement to urllib3>=2.6.3 to ensure downstream consumers (all Foundry sample apps) receive the security patch.

Affected sample apps:

• foundry-sample-collections-toolkit
• foundry-sample-functions-python
• foundry-sample-logscale
• foundry-sample-ngsiem-importer
• foundry-sample-openrouter-toolkit
• foundry-sample-servicenow-idp

This is similar to issue #16 which addressed earlier urllib3 vulnerabilities.