doc: add parameters for settings events
Add parameters for the callback for the Http2Session:localSettings event and Http2Session:remoteSettings event inline with the pattern in the rest of the documentation.
Refs: https://github.com/nodejs/help/issues/877#issuecomment-381253464
Checklist
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make -j4 test
(UNIX), orvcbuild test
(Windows) passes -
documentation is changed or added -
commit message follows commit guidelines
/cc @nodejs/http2 @mcollina @vsemozhetbyt