fix: (formatter) indent after infix lhs

[asterite]

Description

Problem

Resolves #4980

Summary

In reality the new formatter didn't crash anymore, it just formatted this:

fn foo() {
    let x = 1 // one
        + 2 // two
        + 3; // three
}

like this:

fn foo() {
    let x = 1 // one
    + 2 // two
        + 3; // three
}

but making it look like the first snippet was easy, so here's that PR :-)

Additional Context

Documentation

Check one:

• No documentation needed.
• Documentation included in this PR.
• [For Experimental Features] Documentation to be submitted in a separate PR.

PR Checklist

• I have tested the changes locally.
• I have formatted the changes with Prettier and/or cargo fmt on default settings.