RFR: JDK-8276800 Fix table headers in NumericShaper.html [v3]

[Ludvig Janiuk]

> This change introduces no visual difference, but improves a11y.

Ludvig Janiuk has updated the pull request incrementally with one additional commit since the last revision:

  Most idiomatic version so far

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Changes:
  - all: https://git.openjdk.java.net/jdk/pull/6291/files
  - new: https://git.openjdk.java.net/jdk/pull/6291/files/acc9edec..718e36ca

Webrevs:
 - full: https://webrevs.openjdk.java.net/?repo=jdk&pr=6291&range=02
 - incr: https://webrevs.openjdk.java.net/?repo=jdk&pr=6291&range=01-02

  Stats: 4 lines in 1 file changed: 0 ins; 0 del; 4 mod
  Patch: https://git.openjdk.java.net/jdk/pull/6291.diff
  Fetch: git fetch https://git.openjdk.java.net/jdk pull/6291/head:pull/6291

PR: https://git.openjdk.java.net/jdk/pull/6291