docs(secrets): stop implying Personal secrets are shareable

The Copilot code-execution paragraph listed "any secret shared with you as a
Credential Member or Credential Admin" among what mounts, which reads as though
a Personal secret can be shared. It cannot through any product surface:
CredentialMembersSection renders only for workspace secrets and OAuth
credentials, and the personal-credential sync only ever grants the owner.

Narrow the sentence to Workspace grants. The comparison table's "Only you can
use" row for Personal was correct and is left alone.

Co-Authored-By: Claude Opus 5 (1M context) <noreply@anthropic.com>

Author: icecrasher321

apps/docs/content/docs/en/platform/credentials.mdx

@@ -91,7 +91,7 @@ Both masking and model-bound projection match only exact values in either case.
 
 ### Copilot code execution
 
-Copilot's Function and code-execution tools receive a saved secret only when their code explicitly contains a valid `{{KEY}}` reference. Direct `environmentVariables.KEY` access, shell `$KEY`, dynamic names, literals, and configured-but-unused secrets do not mount a value. Code execution requires workspace write access, and the caller must be allowed to **use** the secret — the same set a workflow resolves for them: your own Personal secrets, any secret shared with you as a Credential Member or Credential Admin, and every Workspace secret when you are a workspace admin. A secret you hold no grant on does not mount, and neither does one whose grant is revoked or still pending.
+Copilot's Function and code-execution tools receive a saved secret only when their code explicitly contains a valid `{{KEY}}` reference. Direct `environmentVariables.KEY` access, shell `$KEY`, dynamic names, literals, and configured-but-unused secrets do not mount a value. Code execution requires workspace write access, and the caller must be allowed to **use** the secret — the same set a workflow resolves for them: your own Personal secrets, and Workspace secrets you hold an active grant on as a Credential Member or Credential Admin, which a workspace admin holds on every key. A secret you hold no grant on does not mount, and neither does one whose grant is revoked or still pending.
 
 This matches what a workflow Function block already resolves for the same person, deliberately. Being able to run a secret is not the same as being able to read it: the value stays masked under **Settings → Secrets**, and **See usage** stays visible only to that secret's admins, so a Credential Member using a secret in code is recorded for whoever can rotate it.