Handle BrokenPipe gracefully

[jobarr-amzn]

Description of changes:

Without this, using ion-cli in a pipeline which truncates the output can result in unwanted error output to stderr, e.g.:

❯ ion dump foo.ion | grep "^  timestamp" | cut -w -f 3 | cut -c 2-20 | head -2

2023-07-31T23:11:36
2023-07-31T23:11:36
Error: Os { code: 32, kind: BrokenPipe, message: "Broken pipe" }

Caused by:
    Broken pipe (os error 32)

By handling BrokenPipe gracefully (i.e. ignoring it), we instead see:

❯ ion dump foo.ion | grep "^  timestamp" | cut -w -f 3 | cut -c 2-20 | head -2

2023-07-31T23:11:36
2023-07-31T23:11:36

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By submitting this pull request, I confirm that my contribution is made under the terms of the Apache 2.0 license.

[popematt]

This is a nice fix. Thanks!