Remove leading whitespace from dump-variables-rbc results

For some reason, some internal products were failing the
quick rbc ci check purely because of indentation differences
in the variable dump file. That file has a lot of wonky
leading indentation due to the foreaches and line breaks
in the function implementation that I couldn't figure
out how to remove. Instead, use a sed command to remove
leading spaces after writing the file.

Bug: 239453560
Test: build/bazel/ci/rbc_dashboard.py --quick on a new internal-only product
Change-Id: I4b34d8e0b5dbbfcbb9ed35345d216ca11a5a1198