Use a stable tag for ubuntu in dockerfile (#3231)

## Issue Addressed

N/A

## Proposed Changes

Use stable version of ubuntu base image in dockerfile instead of using latest. This will help in narrowing down issues with docker images.

lcli/Dockerfile

@@ -8,6 +8,6 @@ ARG PORTABLE
 ENV PORTABLE $PORTABLE
 RUN cd lighthouse && make install-lcli
 
-FROM ubuntu:latest
+FROM ubuntu:22.04
 RUN apt-get update && apt-get -y upgrade && apt-get clean && rm -rf /var/lib/apt/lists/*
 COPY --from=builder /usr/local/cargo/bin/lcli /usr/local/bin/lcli