doc: fix incorrect heading level

PR-URL: #35965
Reviewed-By: Colin Ihrig <[email protected]>
Reviewed-By: Anna Henningsen <[email protected]>
Reviewed-By: Antoine du Hamel <[email protected]>
Reviewed-By: Richard Lau <[email protected]>
Reviewed-By: Luigi Pinca <[email protected]>

Author: 700software

doc/api/dns.md

@@ -950,7 +950,7 @@ Here is an example of the result object:
     minttl: 60 } ]
 ```
 
-## `dnsPromises.resolveCaa(hostname)`
+### `dnsPromises.resolveCaa(hostname)`
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