catalog(pass-secrets): declare the real platform matrix

`platforms: []` is not neutral here. The site renders
`plugin.platforms?.length ? … : "Linux, macOS, Windows"`, so the empty list
advertises this entry as working on Windows, which it never has: `pass` is a
`#!/usr/bin/env bash` script (bash + gpg + git + tree) and the source calls it
through `subprocess.run(["pass", ...])` / `shutil.which("pass")`, neither of
which can execute a script on Windows outside WSL/Cygwin/MSYS2. There is no
`fcntl`/`getuid`/`termios` elsewhere in the path — the bash dependency is the
whole constraint.

`linux` and `macos` are both exercised: the GPG store, `pass init`, and the
`.gpg` subdir walk are the same on either.

Entry-only change: `sha` and `version` are untouched, still `485f105` / 1.0.0.
The platform claim is about the package's capability, not about this pin, and
1.0.0 had the same bash dependency.

Related: #146751 carries the same line as part of the 1.1.0 bump. That PR is
blocked on the `/s` sender-gate rework, which is unrelated to this field, so
landing the one-line correction separately keeps a false OS claim off the
listing in the meantime. Whichever merges first, the other needs a one-line
rebase.

plugin-catalog/pass-secrets.yaml

@@ -9,7 +9,7 @@ requires_hermes: ">=0.21.4"
 docs_url: https://github.com/dyiapanis/pass-secrets#readme
 version: "1.0.0"
 readme: true
-platforms: []
+platforms: [linux, macos]
 capabilities:
   provides_tools: []
   provides_hooks: []