Release 2026.8.0-rc6

See https://next.goauthentik.io/docs/releases/2026.8

What's Changed

• stages/authenticator_validate: fix intermittnetly failing throttling test (cherry-pick #24568 to version-2026.8) by @authentik-cherry-pick[bot] in #24708
• ci: sentry-release needs access to metadata. (cherry-pick #24710 to version-2026.8) by @authentik-cherry-pick[bot] in #24711

Full Changelog: version/2026.8.0-rc5...version/2026.8.0-rc6