chore: add tzdata to dockerfile base (#20553)

When deploying Coder using the ghcr.io/coder/coder image, it is not
possible to set the "timezone" field in a preset with an embedded
provisioner. This is due to the container image not having the IANA time
zone database installed, which causes an issue when the terraform
provider attempts to validate the given timezone is valid.

scripts/Dockerfile.base

@@ -12,7 +12,8 @@ RUN apk add --no-cache \
 		bash \
 		git \
 		openssl \
-		openssh-client && \
+		openssh-client \
+		tzdata && \
 	addgroup \
 		-g 1000 \
 		coder && \