Small updates exec_trace.rs

[nikolala13]

Description

Github Repo

https://github.com/nikolala13/zkevm-circuits

[PR description]

Issue Link

[link issue here]

Type of change

• Instead of writing 'f.write_fmt(format_args!(...))', you can use the method 'write!'
• I would also add comments to each Target option explaining their meaning

Contents

• [item]

Rationale

[design decisions and extended information]

How Has This Been Tested?

[explanation]

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MUST: Reference the issue to resolve

Single responsability

Is RECOMMENDED to create single responsibility commits, but not mandatory.

Anyway, you MUST enumerate the changes in a unitary way, e.g.

This PR contains:
- Cleanup of xxxx, yyyy
- Changed xxxx to yyyy in order to bla bla
- Added xxxx function to ...
- Refactored ....

Design choices

RECOMMENDED to:

• What types of design choices did you face?
• What decisions you have made?
• Any valuable information that could help reviewers to think critically