[PATCH resend] doc: format-rev: use [synopsis] on code block

From: Kristoffer Haugsbakk <redacted>

This code block uses the placeholder `<subject>`. Let’s highlight this
placeholder properly by using the `synopsis` block definition which was
introduced in a34d1d53 (doc: convert git-show to synopsis style,
2026-02-06).

Signed-off-by: Kristoffer Haugsbakk <redacted>
---

Notes (series):
    Topic name: kh/doc-format-rev-1

 Documentation/git-format-rev.adoc | 1 +
 1 file changed, 1 insertion(+)

diff --git a/Documentation/git-format-rev.adoc b/Documentation/git-format-rev.adoc
index 505a52feccd..836ba4b0c24 100644
--- a/Documentation/git-format-rev.adoc
+++ b/Documentation/git-format-rev.adoc

@@ -96,6 +96,7 @@ The mode `--stdin-mode=text` replaces each object name with the
 formatted commit, i.e. the format `%s` would transform some commit
 object name to `<subject>` without any termination. Like this:
 
+[synopsis]
 ----
 Did we not fix this in "<subject>"?
 ----

base-commit: e9019fcafe0040228b8631c30f97ae1adb61bcdc
-- 
2.54.0.22.g9e26862b904