Install procps in schema-deployer image (#1934)

It turns out this one uses pgrep and pkill as well, go figure...

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release/schema-deployer/Dockerfile

@@ -31,7 +31,7 @@ RUN apt-get update -y \
     && locale-gen en_US.UTF-8 \
     && apt-get install apt-utils -y \
     && apt-get upgrade -y \
-    && apt-get install openjdk-11-jdk-headless curl -y
+    && apt-get install openjdk-11-jdk-headless curl procps -y
 
 # Get netstat, used for checking Cloud SQL proxy readiness.
 RUN apt-get install net-tools