<Swing Dev> RFR: 8255215: Unsupported 'valign' attribute for 'tr' tag used in j.s.t.h.HTMLDocument

[Prasanta Sadhukhan]

Since HTML4 support has been dropped from javadoc by JDK-8187793.
HTMLDocument.java containing the valign attribute in the table element, `valign="top"` 
needs to be replaced with `style="vertical-align:top"

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Commit messages:
 - 8255215: Unsupported 'valign' attribute for 'tr' tag used in j.s.t.h.HTMLDocument

Changes: https://git.openjdk.java.net/jdk/pull/995/files
 Webrev: https://webrevs.openjdk.java.net/?repo=jdk&pr=995&range=00
  Issue: https://bugs.openjdk.java.net/browse/JDK-8255215
  Stats: 1 line in 1 file changed: 0 ins; 0 del; 1 mod
  Patch: https://git.openjdk.java.net/jdk/pull/995.diff
  Fetch: git fetch https://git.openjdk.java.net/jdk pull/995/head:pull/995

PR: https://git.openjdk.java.net/jdk/pull/995