RFR: JDK-8246351: <code> elements in headings are of incorrect size

[Hannes Wallnöfer]

This is a simple fix to not set the font size and related spacings in `<code>` and `<tt>` elements when they occur inside a heading. The screenshot below shows the new rendered  text in Safari on Mac OS X (there is a `<code>` in the heading and there are several in the flow text).

<img width="699" alt="fontsize" src="https://user-images.githubusercontent.com/15975/120197515-4f97f480-c221-11eb-976a-7bcb040b05ae.png">

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Commit messages:
 - JDK-8246351: <code> elements in headings are of incorrect size

Changes: https://git.openjdk.java.net/jdk/pull/4273/files
 Webrev: https://webrevs.openjdk.java.net/?repo=jdk&pr=4273&range=00
  Issue: https://bugs.openjdk.java.net/browse/JDK-8246351
  Stats: 3 lines in 1 file changed: 3 ins; 0 del; 0 mod
  Patch: https://git.openjdk.java.net/jdk/pull/4273.diff
  Fetch: git fetch https://git.openjdk.java.net/jdk pull/4273/head:pull/4273

PR: https://git.openjdk.java.net/jdk/pull/4273