Theme toggle incorrect display on Firefox with v3

[peterpeterparker]

Have you read the Contributing Guidelines on issues?

• I have read the Contributing Guidelines on issues.

Prerequisites

• I'm using the latest version of Docusaurus.
• I have tried the npm run clear or yarn clear command.
• I have tried rm -rf node_modules yarn.lock package-lock.json and re-installing packages.
• I have tried creating a repro with https://new.docusaurus.io.
• I have read the console error message carefully (if applicable).

Description

Hi,

Just noticed that the theme toggler in the navbar is not correctly displayed on Firefox with Docusaurus v3.
The call to action, instead of displaying a sun or moon, displays both icons.

Firefox:

Chrome for comparison:

Reproducible demo

No response

Steps to reproduce

Open https://new.docusaurus.io in Firefox

Expected behavior

See issue description

Actual behavior

See issue description

Your environment

No response

Self-service

• I'd be willing to fix this bug myself.