RFR: 8345397: Remove <cstdio> from g1HeapRegionRemSet.cpp

[Kim Barrett]

Please review this trivial removal of an unnecessary and improperly placed
include of `<cstdio>`.

Testing: mach5 tier1

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Commit messages:
 - remove unneeded include

Changes: https://git.openjdk.org/jdk/pull/22519/files
  Webrev: https://webrevs.openjdk.org/?repo=jdk&pr=22519&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8345397
  Stats: 2 lines in 1 file changed: 0 ins; 2 del; 0 mod
  Patch: https://git.openjdk.org/jdk/pull/22519.diff
  Fetch: git fetch https://git.openjdk.org/jdk.git pull/22519/head:pull/22519

PR: https://git.openjdk.org/jdk/pull/22519