doc: patch-id: convert to the modern synopsis style

doc: patch-id: convert to the modern synopsis style

Convert this command documentation to the modern synopsis style based on
similar work.[1] Concretely:

• Change the Synopsis section from `verse` to a `synopsis` block which
  will automatically apply the correct formatting to various elements
  (although this Synopsis is very simple)
• Use backticks (`) for code-like things which will also use the correct
  formatting for interior placeholders (`<orderfile>`)
• Use inline-verbatim on options listing

† 1: E.g.,
     • 026f2e3b (doc: convert git-log to new documentation format,
       2025-07-07)
     • b983aaab (doc: convert git-switch manpage to new synopsis style,
       2025-05-25)
     • 16543967 (doc: convert git-mergetool manpage to new synopsis
       style, 2025-05-25)

Signed-off-by: Kristoffer Haugsbakk <code@khaugsbakk.name>
Signed-off-by: Junio C Hamano <gitster@pobox.com>