src: correct indentation for X509ToObject

The indentation in one of the if statements blocks is four spaces
instead of two. This commit changes the indentation to two spaces.

PR-URL: https://github.com/nodejs/node/pull/13543


Reviewed-By: Anna Henningsen <anna@addaleax.net>
Reviewed-By: Colin Ihrig <cjihrig@gmail.com>
Reviewed-By: Michael Dawson <michael_dawson@ca.ibm.com>