RFR: 8261444: Remove unused fields in Lower

[Claes Redestad]

A small code cleanup in Lower, removing a few unused fields.

Last usage of classDollar was removed by JDK-8175191, and dollarCloseResource was removed by JDK-8194978

Testing: tier1-2

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Commit messages:
 - Remove unused fields in Lower

Changes: https://git.openjdk.java.net/jdk/pull/2482/files
 Webrev: https://webrevs.openjdk.java.net/?repo=jdk&pr=2482&range=00
  Issue: https://bugs.openjdk.java.net/browse/JDK-8261444
  Stats: 8 lines in 1 file changed: 0 ins; 8 del; 0 mod
  Patch: https://git.openjdk.java.net/jdk/pull/2482.diff
  Fetch: git fetch https://git.openjdk.java.net/jdk pull/2482/head:pull/2482

PR: https://git.openjdk.java.net/jdk/pull/2482