chore(oidc): graduate webkey to stable (#10122)

# Which Problems Are Solved

Stabilize the usage of webkeys.

# How the Problems Are Solved

- Remove all legacy signing key code from the OIDC API
- Remove the webkey feature flag from proto
- Remove the webkey feature flag from console
- Cleanup documentation

# Additional Changes

- Resolved some canonical header linter errors in OIDC
- Use the constant for `projections.lock` in the saml package.

# Additional Context

- Closes #10029
- After #10105
- After #10061

console/src/assets/i18n/en.json

@@ -1645,8 +1645,6 @@
       "ENABLEBACKCHANNELLOGOUT_DESCRIPTION": "The Back-Channel Logout implements OpenID Connect Back-Channel Logout 1.0 and can be used to notify clients about session termination at the OpenID Provider.",
       "PERMISSIONCHECKV2": "Permission Check V2",
       "PERMISSIONCHECKV2_DESCRIPTION": "If the flag is enabled, you'll be able to use the new API and its features.",
-      "WEBKEY": "Web Key",
-      "WEBKEY_DESCRIPTION": "If the flag is enabled, you'll be able to use the new API and its features.",
       "STATES": {
         "INHERITED": "Inherit",
         "ENABLED": "Enabled",