Clarify that .rbenv-version is removed when migrating

libexec/rbenv-local

@@ -38,8 +38,10 @@ if [ "$RBENV_VERSION" = "--unset" ]; then
   rm -f .ruby-version .rbenv-version
 elif [ -n "$RBENV_VERSION" ]; then
   if [ "$(RBENV_VERSION= rbenv-version-origin)" -ef .rbenv-version ]; then
-    echo "rbenv: migrated .rbenv-version file to .ruby-version" >&2
     rm -f .rbenv-version
+    { echo "rbenv: removed existing \`.rbenv-version' file and migrated"
+      echo "       local version specification to \`.ruby-version' file"
+    } >&2
   fi
   rbenv-version-file-write .ruby-version "$RBENV_VERSION"
 else