changelog: rename changelog file to reflect the number of the related issue

Signed-off-by: Valerio Setti <valerio.setti@nordicsemi.no>
diff --git a/ChangeLog.d/8664.txt b/ChangeLog.d/8340.txt
similarity index 100%
rename from ChangeLog.d/8664.txt
rename to ChangeLog.d/8340.txt