RFR: 8356656: Drop unused DEVKIT_HOME from jib-profiles.js

[Mikael Vidstedt]

The DEVKIT_HOME environment variable gets set up in jib-profiles.js but the last use of it was removed in [JDK-8264805](https://bugs.openjdk.org/browse/JDK-8264805).

Testing: tier1,builds-tier[2-5]

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Commit messages:
 - 8356656: Drop unused DEVKIT_HOME from jib-profiles.js

Changes: https://git.openjdk.org/jdk/pull/25159/files
  Webrev: https://webrevs.openjdk.org/?repo=jdk&pr=25159&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8356656
  Stats: 18 lines in 3 files changed: 14 ins; 3 del; 1 mod
  Patch: https://git.openjdk.org/jdk/pull/25159.diff
  Fetch: git fetch https://git.openjdk.org/jdk.git pull/25159/head:pull/25159

PR: https://git.openjdk.org/jdk/pull/25159