RFR: 8266505: Cleanup LibraryCallKit::make_unsafe_address()

[Roman Kennke]

The decorators argument to make_unsafe_address() is unused and can be removed. It's a leftover from when Shenandoah needed to resolve the target object there. 

Testing:
 - [x] hotspot_gc_shenandoah
 - [x] tier1
 - [x] tier2

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Commit messages:
 - 8266505: Cleanup LibraryCallKit::make_unsafe_address()

Changes: https://git.openjdk.java.net/jdk/pull/3858/files
 Webrev: https://webrevs.openjdk.java.net/?repo=jdk&pr=3858&range=00
  Issue: https://bugs.openjdk.java.net/browse/JDK-8266505
  Stats: 11 lines in 3 files changed: 0 ins; 1 del; 10 mod
  Patch: https://git.openjdk.java.net/jdk/pull/3858.diff
  Fetch: git fetch https://git.openjdk.java.net/jdk pull/3858/head:pull/3858

PR: https://git.openjdk.java.net/jdk/pull/3858