[jdk13u-dev] RFR: 8264108: Update version .jcheck/conf in jdk13u-dev to be 13.0.8

[Yuri Nesterenko]

I hope that with this change all subsequent fixes (until July 2021) will have fixVersion 13.0.8

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Commit messages:
 - 8264108: Update version .jcheck/conf in jdk13u-dev to be 13.0.8

Changes: https://git.openjdk.java.net/jdk13u-dev/pull/161/files
 Webrev: https://webrevs.openjdk.java.net/?repo=jdk13u-dev&pr=161&range=00
  Issue: https://bugs.openjdk.java.net/browse/JDK-8264108
  Stats: 1 line in 1 file changed: 0 ins; 0 del; 1 mod
  Patch: https://git.openjdk.java.net/jdk13u-dev/pull/161.diff
  Fetch: git fetch https://git.openjdk.java.net/jdk13u-dev pull/161/head:pull/161

PR: https://git.openjdk.java.net/jdk13u-dev/pull/161