Correct handle of global imports over multiple lines in ./src/prepare.ts

[oxe-i]

The code in ./src/prepare.ts wasn't deleting/commenting out jest global imports over multiple lines. Added a fix.

[oxe-i]

@SleeplessByte As discussed on https://forum.exercism.org/t/redeclaration-of-import-beforeeach-error-in-robot-name/18581/9

[oxe-i]

Reverted back to indexOf as it doesn't seem to matter for the test and as the global import was already commented out before.

But I believe that right now the text is injected after the first from which can be the one from the global imports (now commented out). So not necessarily after the main import.

[oxe-i]

@SleeplessByte Committed the change you suggested. Do I need to do anything more?

[SleeplessByte]

@oxe-i thanks! Nope, just going to do another fix and then I'll merge both together