fix: Hide network fee fiat conversion on test nets

[pedronfigueiredo]

Description

This PR introduces a missing parenthesis in the display logic.

Related issues

Fixes: https://github.com/MetaMask/MetaMask-planning/issues/4147

Manual testing steps

1. Go to this page...

Screenshots/Recordings

Before

After

Pre-merge author checklist

• I've followed MetaMask Contributor Docs and MetaMask Extension Coding Standards.
• I've completed the PR template to the best of my ability
• I’ve included tests if applicable
• I’ve documented my code using JSDoc format if applicable
• I’ve applied the right labels on the PR (see labeling guidelines). Not required for external contributors.

Pre-merge reviewer checklist

• I've manually tested the PR (e.g. pull and build branch, run the app, test code being changed).
• I confirm that this PR addresses all acceptance criteria described in the ticket it closes and includes the necessary testing evidence such as recordings and or screenshots.

[github-actions]

CLA Signature Action: All authors have signed the CLA. You may need to manually re-run the blocking PR check if it doesn't pass in a few minutes.

[metamaskbot]

Builds ready [afa28a5]

• builds: chrome, firefox
• builds (flask): chrome, firefox
• builds (MMI): chrome
• builds (test): chrome, firefox
• builds (test-flask): chrome, firefox
• build viz: Build System
• mv3: Bundle Size Stats
• mv2: E2e Actions Stats
• storybook: Storybook
• typescript migration: Dashboard
• all artifacts
• bundle viz:

  • background: 0, 1, 2, 3, 4, 5, 6, 7
  • common: 0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13
  • ui: 0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12
  • content-script: 0
  • offscreen: 0

Page Load Metrics (1754 ± 156 ms)

Platform	Page	Metric	Min (ms)	Max (ms)	Average (ms)	StandardDeviation (ms)	MarginOfError (ms)
Chrome	Home	firstPaint	381	2253	1568	457	220
		domContentLoaded	1430	2681	1727	329	158
		load	1434	2692	1754	325	156
		domInteractive	21	69	39	17	8
		backgroundConnect	8	224	33	46	22
		firstReactRender	14	76	38	24	11
		getState	4	62	13	16	8
		initialActions	0	1	0	0	0
		loadScripts	1021	2028	1253	253	121
		setupStore	7	56	14	14	7
		uiStartup	1602	3047	1985	372	178

Bundle size diffs

• background: 0 Bytes (0.00%)
• ui: 6 Bytes (0.00%)
• common: 0 Bytes (0.00%)