Bump Go toolchain to 1.26.6 to fix stdlib security vulnerabilities

[shwetamurali]

Description

Bumps the Go toolchain from 1.26.4 to 1.26.6 to resolve multiple security vulnerabilities in the Go standard library. The reported vulnerabilities are reachable through the standard library. The fix is a toolchain version bump.

PR Checklist

• Run npx changie new or install changie to prepare a new changelog entry for the next set of release notes.
• Ensure any command changes are sensitive to these global flags:
  • --json — Force machine readable output to stdout. Does not apply to stderr.
  • --markdown — Force markdown output to stdout. Does not apply to stderr.
  • --dry-run — Don't make any actual writes or other mutations. Describe what would have changed to stderr.
  • --quiet — Only render essential content.
• Get the logging interface from the context and add debug logging for interesting conditions and nonfatal situations.
• Run make gen/screenshot if the root command output changes.
• Add the Autocomplete field to positional arguments and flags to assist shell autocomplete.

PCI review checklist

• I have documented a clear reason for, and description of, the change I am making.

• If applicable, I've documented a plan to revert these changes if they require more than reverting the pull request.

• If applicable, I've documented the impact of any changes to security controls.

  Examples of changes to security controls include using new access control methods, adding or removing logging pipelines, etc.