Minor corrections to Http2 example javadocs.

Motivation:
There are a few very minor issues in the Http2 examples javadoc and
since I don't think that these javadocs are published this is very much
optional to include.

Modifications:
Updated the @see according to [1] to avoid warning when generating
javadocs.

Result:
No warning when generating javadocs.

[1] http://docs.oracle.com/javase/1.5.0/docs/tooldocs/windows/javadoc.html#@see
I was not sure and just left the tag there to be consistent with the previous ```@see```. I'll remove them.