doc: mention that --stats is always implied by --json

Fixes #2337

CHANGELOG.md

@@ -75,6 +75,8 @@ Bug fixes:
   Fix gitignore parsing bug where a trailing `\/` resulted in an error.
 * [BUG #2243](https://github.com/BurntSushi/ripgrep/issues/2243):
   Fix `--sort` flag for values other than `path`.
+* [BUG #2337](https://github.com/BurntSushi/ripgrep/issues/2337):
+  Improve docs to mention that `--stats` is always implied by `--json`.
 * [BUG #2381](https://github.com/BurntSushi/ripgrep/issues/2381):
   Make `-p/--pretty` override flags like `--no-line-number`.
 * [BUG #2392](https://github.com/BurntSushi/ripgrep/issues/2392):

crates/core/flags/defs.rs

@@ -3392,7 +3392,8 @@ flags are used in concert with \flag{json}.
 .sp
 Other flags that control aspects of the standard output such as
 \flag{only-matching}, \flag{heading}, \flag{replace}, \flag{max-columns}, etc.,
-have no effect when \flag{json} is set.
+have no effect when \flag{json} is set. However, enabling JSON output will
+always implicitly and unconditionally enable \flag{stats}.
 .sp
 A more complete description of the JSON format used can be found here:
 \fIhttps://docs.rs/grep-printer/*/grep_printer/struct.JSON.html\fP.
@@ -6420,6 +6421,8 @@ complete.
 .sp
 This set of aggregate statistics may expand over time.
 .sp
+This flag is always and implicitly enabled when \flag{json} is used.
+.sp
 Note that this flag has no effect if \flag{files}, \flag{files-with-matches} or
 \flag{files-without-match} is passed.
 "