Add deprecated comment on `displayWarning`

[OGPoyraz]

Description

This PR aims to mark displayWarning as deprecated.

Related issues

N/A

Manual testing steps

No functional change

Screenshots/Recordings

N/A

Before

N/A

After

N/A

Pre-merge author checklist

• [ ] I’ve followed MetaMask Coding Standards.
• [ ] I've clearly explained what problem this PR is solving and how it is solved.
• [ ] I've linked related issues
• [ ] I've included manual testing steps
• [ ] I've included screenshots/recordings if applicable
• [ ] 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.
• [ ] I’ve properly set the pull request status:
  • [ ] In case it's not yet "ready for review", I've set it to "draft".
  • [ ] In case it's "ready for review", I've changed it from "draft" to "non-draft".

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.

[Gudahtt]

Comment originally added here: #17465, but it was accidentally removed later.

[codecov[bot]]

Codecov Report

All modified and coverable lines are covered by tests :white_check_mark:

Comparison is base (3e00753) 68.44% compared to head (1518ca3) 68.44%. Report is 6 commits behind head on develop.

Additional details and impacted files

@@           Coverage Diff            @@
##           develop   #22853   +/-   ##
========================================
  Coverage    68.44%   68.44%           
========================================
  Files         1089     1089           
  Lines        42899    42899           
  Branches     11427    11427           
========================================
  Hits         29362    29362           
  Misses       13537    13537           

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[metamaskbot]

Builds ready [1518ca3]

• builds: chrome, firefox
• builds (beta): chrome
• builds (flask): chrome, firefox
• builds (MMI): chrome, firefox
• builds (test): chrome, firefox
• builds (test-flask): chrome, firefox
• build viz: Build System
• mv3: Background Module Init Stats
• mv3: UI Init Stats
• mv3: Module Load Stats
• mv3: Bundle Size Stats
• mv2: E2e Actions Stats
• code coverage: Report
• storybook: Storybook
• typescript migration: Dashboard
• all artifacts
• bundle viz:

  • background: 0, 1, 2, 3, 4
  • common: 0, 1, 2, 3, 4, 5, 6, 7
  • content-script: 0
  • contentscript: contentscript
  • disable-console: disable-console
  • inpage: inpage
  • policy-load: policy-load
  • sentry-install: sentry-install
  • ui: 0, 1, 10, 11, 2, 3, 4, 5, 6, 7, 8, 9

Page Load Metrics (818 ± 26 ms)

Platform	Page	Metric	Min (ms)	Max (ms)	Average (ms)	StandardDeviation (ms)	MarginOfError (ms)
Chrome	Home	firstPaint	94	148	110	15	7
		domContentLoaded	9	48	20	8	4
		load	744	935	818	54	26
		domInteractive	9	48	20	8	4

Bundle size diffs

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