RFR: 8319607: FFM: Review the language in the FFM documentation

[Per Minborg]

This PR proposes to improve the language used in the FFM specification. There is a relatively small number of corrections.

One peculiarity with the English language is the distinction between "that" (to be used in a restrictive clause) and "which" (to be used in a non-restrictive clause). Here is a reference: https://preply.com/en/blog/when-to-use-which-or-that-the-most-common-cases

Another source for updates is the difference between BE and AE where most of us Europeans were taught BE but we should use AE in the specifications.

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Commit messages:
 - Change to AE in a word
 - Improve language in the FFM specification

Changes: https://git.openjdk.org/jdk/pull/16536/files
 Webrev: https://webrevs.openjdk.org/?repo=jdk&pr=16536&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8319607
  Stats: 128 lines in 12 files changed: 0 ins; 0 del; 128 mod
  Patch: https://git.openjdk.org/jdk/pull/16536.diff
  Fetch: git fetch https://git.openjdk.org/jdk.git pull/16536/head:pull/16536

PR: https://git.openjdk.org/jdk/pull/16536