chore: unhide 'scim-use-legacy' flag (#26465)

cli/testdata/coder_server_--help.golden

@@ -982,5 +982,9 @@ These options are only available in the Enterprise Edition.
           Enables SCIM and sets the authentication header for the built-in SCIM
           server. New users are automatically created with OIDC authentication.
 
+      --scim-use-legacy bool, $CODER_SCIM_USE_LEGACY (default: true)
+          Use the legacy SCIM implementation instead of the SCIM 2.0 handler.
+          This is provided for backward compatibility for existing users.
+
 ———
 Run `coder --help` for a list of global options.

cli/testdata/server-config.yaml.golden

@@ -519,6 +519,10 @@ sshKeygenAlgorithm: ed25519
 # URL to use for agent troubleshooting when not set in the template.
 # (default: https://coder.com/docs/admin/templates/troubleshooting, type: url)
 agentFallbackTroubleshootingURL: https://coder.com/docs/admin/templates/troubleshooting
+# Use the legacy SCIM implementation instead of the SCIM 2.0 handler. This is
+# provided for backward compatibility for existing users.
+# (default: true, type: bool)
+scimUseLegacy: true
 # Disable workspace apps that are not served from subdomains. Path-based apps can
 # make requests to the Coder API and pose a security risk when the workspace
 # serves malicious JavaScript. This is recommended for security purposes if a