[jdk17u-dev] RFR: 8310915: Typo in aarch64.ad: "envcodings"

[Elif Aslan]

Clean backport. This is a trivial update to a comment that starts with an unnecessary extra slash and contains a typo.

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Commit messages:
 - Backport 6f325db49365d3d06add5d194d4696a1428675fa

Changes: https://git.openjdk.org/jdk17u-dev/pull/4165/files
  Webrev: https://webrevs.openjdk.org/?repo=jdk17u-dev&pr=4165&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8310915
  Stats: 1 line in 1 file changed: 0 ins; 0 del; 1 mod
  Patch: https://git.openjdk.org/jdk17u-dev/pull/4165.diff
  Fetch: git fetch https://git.openjdk.org/jdk17u-dev.git pull/4165/head:pull/4165

PR: https://git.openjdk.org/jdk17u-dev/pull/4165