RFR: 8338595: Add more linesize for MIME decoder in macro bench test Base64Decode

[Hamlin Li]

Hi,
Can you help to review this simple patch?

Currently, lineSize linesize for MIME case in macro bench test Base64Decode is only "4", but in Base64.Encoder default linesize for MIME encoder is 76.
It's helpful to add more linesize, e.g. 76 and so on.

Thanks!

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Commit messages:
 - Initial commit

Changes: https://git.openjdk.org/jdk/pull/20630/files
  Webrev: https://webrevs.openjdk.org/?repo=jdk&pr=20630&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8338595
  Stats: 1 line in 1 file changed: 0 ins; 0 del; 1 mod
  Patch: https://git.openjdk.org/jdk/pull/20630.diff
  Fetch: git fetch https://git.openjdk.org/jdk.git pull/20630/head:pull/20630

PR: https://git.openjdk.org/jdk/pull/20630