Error message when updating firefox

[Rick429CJ]

When I last updated Firefox, I got this message:

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W: Target Packages (main/binary-amd64/Packages) is configured multiple times in /etc/apt/sources.list.d/mozilla.list:1 and /etc/apt/sources.list.d/mozilla.list:2
W: Target Packages (main/binary-i386/Packages) is configured multiple times in /etc/apt/sources.list.d/mozilla.list:1 and /etc/apt/sources.list.d/mozilla.list:2
W: Target Packages (main/binary-all/Packages) is configured multiple times in /etc/apt/sources.list.d/mozilla.list:1 and /etc/apt/sources.list.d/mozilla.list:2
W: Target Translations (main/i18n/Translation-en_NZ) is configured multiple times in /etc/apt/sources.list.d/mozilla.list:1 and /etc/apt/sources.list.d/mozilla.list:2
W: Target Translations (main/i18n/Translation-en) is configured multiple times in /etc/apt/sources.list.d/mozilla.list:1 and /etc/apt/sources.list.d/mozilla.list:2
How do I fix it?