RFR: 8261004: java.util.Formatter throws wrong exception for mismatched flags in %% conversion

Updating the specification to reflect well-established behavior in Formatter when incorrect flags used for `%`. ------------- Commit messages: - Changing docs to reflect behavior Changes: https://git.openjdk.java.net/jdk/pull/2389/files Webrev: https://webrevs.openjdk.java.net/?repo=jdk&pr=2389&range=00 Issue: https://bugs.openjdk.java.net/browse/JDK-8261004 Stats: 1 line in 1 file changed: 0 ins; 0 del; 1 mod Patch: https://git.openjdk.java.net/jdk/pull/2389.diff Fetch: git fetch https://git.openjdk.java.net/jdk pull/2389/head:pull/2389 PR: https://git.openjdk.java.net/jdk/pull/2389