RFR: 8319231: Unrecognized "minimum" key in .jcheck/conf causes /reviewers command to be ignored

[Kevin Rushforth]

A recent change to Skara in processing of the .jcheck/conf file ([SKARA-2080](https://bugs.openjdk.org/browse/SKARA-2080)) introduced a bug in processing the `[checks "reviewers"]` section that causes the `/reviewers` command to be ignored in some cases. This is tracked by [SKARA-2088](https://bugs.openjdk.org/browse/SKARA-2088). The reason we tripped over this bug is that the `.jcheck/conf` file used by jfx (including various update release repos) uses an unrecognized key, "minimum", instead of the expected "reviewers" key to indicate the minimum number of reviewers. We should fix this to be consistent with what Skara expects given the intent of our `[checks "reviewers"]` section.

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Commit messages:
 - 8319231: Unrecognized "minimum" key in .jcheck/conf causes /reviewers command to be ignored

Changes: https://git.openjdk.org/jfx/pull/1275/files
 Webrev: https://webrevs.openjdk.org/?repo=jfx&pr=1275&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8319231
  Stats: 1 line in 1 file changed: 0 ins; 0 del; 1 mod
  Patch: https://git.openjdk.org/jfx/pull/1275.diff
  Fetch: git fetch https://git.openjdk.org/jfx.git pull/1275/head:pull/1275

PR: https://git.openjdk.org/jfx/pull/1275