golang: bump 1.26 to 1.26.6 - #30278

Checking PR #30278: golang: bump 1.26 to 1.26.6 (Formalities Audit)

✅ Pull request originates from a dedicated feature branch (25.12/golang-bump-to-1.26.6)

Commit f5f3683 - golang: bump 1.26 to 1.26.6:

✅ Author and committer identities are valid
✅ Commit is not a merge commit
✅ Commit subject layout and length are valid: "golang: bump 1.26 to 1.26.6"
✅ Commit description lines adhere to width formatting rules
✅ Commit contains a valid 'Signed-off-by:' line matching author or committer
⚠️ Warning: Commit is unsigned or cryptographic signature verification failed (Reason: unsigned). Signing commits is a recommended best practice for verifying identity, but is not mandatory.
✅ Commit explicitly specifies cherry-pick origin context
✅ Backport matches upstream commit verbatim. Skipping style and packaging validations.