Fix unused result warning in node_url.cc (nit)

[brodycj]

Checklist

• make -j8 test (UNIX), or vcbuild test nosign (Windows) passes
• commit message follows commit guidelines

Affected core subsystem(s)

url

Description of change

Mark ignored return value in node::url::Parse(...) with (void).

This is to resolve an unused result warning in node_url.cc.

[brodycj]

This fix will be submitted as part of a bigger change set ref: #9767 (comment)