[no ci - doxygen] don't elevate warnings as errors

Doxyfile

@@ -796,7 +796,7 @@ WARN_NO_PARAMDOC       = NO
 # a warning is encountered.
 # The default value is: NO.
 
-WARN_AS_ERROR          = YES
+WARN_AS_ERROR          = NO
 
 # The WARN_FORMAT tag determines the format of the warning messages that doxygen
 # can produce. The string should contain the $file, $line, and $text tags, which