model archiver example to multi-line

[GeeCastro]

Description

Changes torch model archiver example to a multi-line readable block

Fixes #3154

Type of change

Please delete options that are not relevant.

• This change requires a documentation update

Feature/Issue validation/testing

Simple line split with \ bash style

Checklist:

• Did you have fun?
• Have you added tests that prove your fix is effective or that this feature works?
• Has code been commented, particularly in hard-to-understand areas?
• Have you made corresponding changes to the documentation?

[mreso]

LGTM, thanks for the contribution and sorry for the delayed review.