RFR: docs JDK-8220261: fix headings in java.base

[Lance Andersen]

Hi Jon,

I went through the patch and it looks good (matches what i did for java.sql.rowset and java.naming :-) )

> On Mar 20, 2019, at 5:50 PM, Jonathan Gibbons <jonathan.gibbons at oracle.com> wrote:
> 
> JDK-8220248

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 <http://oracle.com/us/design/oracle-email-sig-198324.gif>Lance Andersen| Principal Member of Technical Staff | +1.781.442.2037
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