build-unit-test-docker: turn 'pip3 install' calls into one invocation

Future Ubuntu is going to require us to pass in a parameter to
`pip3 install`.  Reduce the number of RUN commands to simplify that
future invocation.

Signed-off-by: Patrick Williams <patrick@stwcx.xyz>
Change-Id: I9f5d4d6b43c637dbfeb6beaadfb5bf80f82cefc3
diff --git a/scripts/build-unit-test-docker b/scripts/build-unit-test-docker
index 87a565d..3957250 100755
--- a/scripts/build-unit-test-docker
+++ b/scripts/build-unit-test-docker
@@ -839,17 +839,18 @@
 """
 
 dockerfile_base += """
-RUN pip3 install beautysh
-RUN pip3 install black
-RUN pip3 install codespell
-RUN pip3 install flake8
-RUN pip3 install gitlint
-RUN pip3 install inflection
-RUN pip3 install isort
-RUN pip3 install jsonschema
-RUN pip3 install meson==0.63.0
-RUN pip3 install protobuf
-RUN pip3 install requests
+RUN pip3 install \
+        beautysh \
+        black \
+        codespell \
+        flake8 \
+        gitlint \
+        inflection \
+        isort \
+        jsonschema \
+        meson==0.63.0 \
+        protobuf \
+        requests
 
 RUN npm install -g \
         eslint@latest eslint-plugin-json@latest \