Fix typo in (cache-check-probablity)

I was trying to use it as documented here, but there is a typo when used as a config file entry (the cmdline entry seems fine):
https://dune.readthedocs.io/en/stable/caching.html#reproducibility-check

Signed-off-by: Edwin Török <edvin.torok@citrix.com>

src/dune/config.ml

@@ -263,7 +263,7 @@ let decode =
       (Dune_lang.Syntax.since Stanza.syntax (2, 0) >>> Caching.Transport.decode)
       ~default:default.cache_transport
   and+ cache_check_probability =
-    field "cache-check-probablity"
+    field "cache-check-probability"
       (Dune_lang.Syntax.since Stanza.syntax (2, 0) >>> Dune_lang.Decoder.float)
       ~default:default.cache_check_probability
   and+ cache_duplication =