chore(deps): update us.gcr.io/celo-org/geth docker tag to v1.8.4

Signed-off-by: renovate[bot] <29139614+renovate[bot]@users.noreply.github.com>

Author: renovate[bot]

Dockerfile

@@ -46,7 +46,7 @@ RUN go build --tags musl -o rosetta .
 # Outputs: rosetta & geth binaries on /usr/loca/bin
 #---------------------------------------------------------------------
 # geth mainnet
-FROM us.gcr.io/celo-org/geth:1.8.2
+FROM us.gcr.io/celo-org/geth:1.8.4
 
 ARG COMMIT_SHA