Fix bug with comment for inline table key

[i1i1]

Motivation

If workspace features dependency and workspace crate uses it, it is always gets merged as regular table (not inline one) so comments ends up in the following position:

[
            # arbitrary
            dependencies.arbitrary ]

Take a look at the test for more info.

Fixes #527

Checklist

• added tests to verify new behavior
• added an example template or updated an existing one
• updated docs/API.md (or general documentation) with changes
• updated CHANGELOG.md

[ipetkov]

Thanks for addressing this, totally didn't realize toml_edit supported clearing comments like this! It also appears to resolve #527