arm: dts: sawshark: fix nonexistent metadata partition

/dev/block/platform/soc/7824900.sdhci/by-name/metadata does not exist.
It is safe to just omit it.

Bug: 77997040
Change-Id: I9d7b7c027fddfd568596ebcab7c66c6f93befb94
Signed-off-by: Ben Fennema <fennema@google.com>