build-unit-test-docker: Protobuf versions should match

The python protobuf version should match the compiler and library
version, or else we will run into API issues.

Change-Id: Iba9472123734cb1015c0d2f0dc72bd18be660355
Signed-off-by: William A. Kennington III <wak@google.com>
diff --git a/scripts/build-unit-test-docker b/scripts/build-unit-test-docker
index 80e1dda..a34552c 100755
--- a/scripts/build-unit-test-docker
+++ b/scripts/build-unit-test-docker
@@ -816,6 +816,7 @@
     python3-git \
     python3-mako \
     python3-pip \
+    python3-protobuf \
     python3-setuptools \
     python3-socks \
     python3-yaml \
@@ -866,7 +867,6 @@
         isort \
         jsonschema \
         meson==1.3.0 \
-        protobuf \
         requests
 
 RUN npm install -g \