docs: Fix singing -> signing typos (#45122)

docs/pages/reference/join-methods.mdx

@@ -88,7 +88,7 @@ for an instance to join the cluster.
 
 Secret-based join methods are universal: Teleport service can use a secret-based
 join method regardless of the platform/cloud provider it runs on. The joining instance
-sends the secret and the Auth Service validates that it matches the one it 
+sends the secret and the Auth Service validates that it matches the one it
 knows. Those joining methods are inherently prone to secret exfiltration and
 the delegated join methods should be preferred when available. If you have
 to use a secret-based join method, it is recommended to use short-lived tokens
@@ -139,7 +139,7 @@ Renewable join-methods are:
 - [static `token`](#static-tokens)
 - [`ec2`](#aws-ec2-identity-document-ec2)
 
-Nodes with non-renewable certificates must join again in order to get a new 
+Nodes with non-renewable certificates must join again in order to get a new
 certificate before expiry. The instance will have to prove again that it is legitimate.
 The non-renewable join methods guarantee that an attacker stealing the instance
 certificates will not be able to maintain access to the Teleport cluster.
@@ -173,7 +173,7 @@ spec:
   # - edit the token to update the roles (e.g. add "App")
   # - un-register the Teleport instance
   # - modify its configuration to enable the new service (here "app_service.enabled")
-  # - have the instance join again 
+  # - have the instance join again
   #
   # You should use the minimal set of system roles required.
   # Common roles are:
@@ -185,7 +185,7 @@ spec:
   # - "WindowsDesktop" for Windows Desktop Service
   # - "Discovery" for Discovery Service
   # - "Bot" for MachineID (when set, "spec.bot_name" must be set in the token)
-  roles: 
+  roles:
     - Node
     - App
   join_method: gcp
@@ -409,7 +409,7 @@ The Kubernetes JWKS join method is available in Teleport 14+.
 
 <Admonition type="warning">
 After rotating the Kubernetes CA, you must update the Kubernetes JWKS tokens
-to contain the new Kubernetes singing keys (update the
+to contain the new Kubernetes signing keys (update the
 `spec.kubernetes.static_jwks.jwks` field).
 </Admonition>