RFR: JDK-8276236: Table headers missing in Formatter api docs

[Ludvig Janiuk]

Adds table headers to all tables in Formatter api docs. I inferred the header "Unicode" for the columns that contained unicode
codepoints.

Formatter api docs: https://docs.oracle.com/en/java/javase/17/docs/api/java.base/java/util/Formatter.html

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Commit messages:
 - Fixes JDK-8276236

Changes: https://git.openjdk.java.net/jdk/pull/6195/files
 Webrev: https://webrevs.openjdk.java.net/?repo=jdk&pr=6195&range=00
  Issue: https://bugs.openjdk.java.net/browse/JDK-8276236
  Stats: 80 lines in 1 file changed: 80 ins; 0 del; 0 mod
  Patch: https://git.openjdk.java.net/jdk/pull/6195.diff
  Fetch: git fetch https://git.openjdk.java.net/jdk pull/6195/head:pull/6195

PR: https://git.openjdk.java.net/jdk/pull/6195