Fix the image of firestore-emulator

[knanao]

What this PR does / why we need it:
I faced an error like the one below.
This is thought to be caused by some omission in the configuration but we were able to avoid this by using google-sdk base image. Hence I applied.

Executing: /usr/local/google-cloud-sdk/platform/cloud-firestore-emulator/cloud_firestore_emulator start --host=0.0.0.0 --port=8080
ERROR: gcloud crashed (FileNotFoundError): [Errno 2] No such file or directory: '/usr/local/google-cloud-sdk/platform/cloud-firestore-emulator/cloud_firestore_emulator': '/usr/local/google-cloud-sdk/platform/cloud-firestore-emulator/cloud_firestore_emulator'

If you would like to report this issue, please run the following command:
  gcloud feedback

To check gcloud for common problems, please run the following command:
  gcloud info --run-diagnostics

Which issue(s) this PR fixes:

Fixes #

Does this PR introduce a user-facing change?:

NONE

[nghialv]

👍

[khanhtc1202]

Here you go 🐰