[ci] Remove tools from Dockerfile (flutter#4649)

Remove the Firebase Test Lab tools from the Dockerfile, since we are no longer running FTL tests in Cirrus.

Author: stuartmorgan-g

.ci/Dockerfile

@@ -4,13 +4,3 @@
 FROM cirrusci/flutter@sha256:d99b1ba2602240a74722970b5c0cd704bbe60a7eba7557157c784f2f693c393f
 
 RUN apt-get update -y
-
-# Set up Firebase Test Lab requirements.
-RUN apt-get install -y --no-install-recommends gnupg
-RUN echo "deb [signed-by=/usr/share/keyrings/cloud.google.gpg] https://packages.cloud.google.com/apt cloud-sdk main" | \
-    sudo tee -a /etc/apt/sources.list.d/google-cloud-sdk.list
-RUN curl https://packages.cloud.google.com/apt/doc/apt-key.gpg | \
-    sudo apt-key --keyring /usr/share/keyrings/cloud.google.gpg add -
-RUN apt-get update && apt-get install -y google-cloud-sdk && \
-    gcloud config set core/disable_usage_reporting true && \
-    gcloud config set component_manager/disable_update_check true