Fix downloads.json for 12.5 (tor-browser-build#40890)

Set the version as a string instead of a number.

update_1/release/download-linux-x86_64.json

-{"binary":"https://cdn.mullvad.net/browser/12.5/mullvad-browser-linux64-12.5_ALL.tar.xz","git_tag":"tbb-12.5-build1","sig":"https://cdn.mullvad.net/browser/12.5/mullvad-browser-linux64-12.5_ALL.tar.xz.asc","version":12.5}
\ No newline at end of file
+{"binary":"https://cdn.mullvad.net/browser/12.5/mullvad-browser-linux64-12.5_ALL.tar.xz","git_tag":"tbb-12.5-build1","sig":"https://cdn.mullvad.net/browser/12.5/mullvad-browser-linux64-12.5_ALL.tar.xz.asc","version":"12.5"}
\ No newline at end of file

update_1/release/download-macos.json

-{"binary":"https://cdn.mullvad.net/browser/12.5/MullvadBrowser-12.5-macos_ALL.dmg","git_tag":"tbb-12.5-build1","sig":"https://cdn.mullvad.net/browser/12.5/MullvadBrowser-12.5-macos_ALL.dmg.asc","version":12.5}
\ No newline at end of file
+{"binary":"https://cdn.mullvad.net/browser/12.5/MullvadBrowser-12.5-macos_ALL.dmg","git_tag":"tbb-12.5-build1","sig":"https://cdn.mullvad.net/browser/12.5/MullvadBrowser-12.5-macos_ALL.dmg.asc","version":"12.5"}
\ No newline at end of file

update_1/release/download-windows-x86_64.json

-{"binary":"https://cdn.mullvad.net/browser/12.5/mullvadbrowser-install-win64-12.5_ALL.exe","git_tag":"tbb-12.5-build1","sig":"https://cdn.mullvad.net/browser/12.5/mullvadbrowser-install-win64-12.5_ALL.exe.asc","version":12.5}
\ No newline at end of file
+{"binary":"https://cdn.mullvad.net/browser/12.5/mullvadbrowser-install-win64-12.5_ALL.exe","git_tag":"tbb-12.5-build1","sig":"https://cdn.mullvad.net/browser/12.5/mullvadbrowser-install-win64-12.5_ALL.exe.asc","version":"12.5"}
\ No newline at end of file

update_1/release/downloads.json

-{"downloads":{"linux64":{"ALL":{"binary":"https://cdn.mullvad.net/browser/12.5/mullvad-browser-linux64-12.5_ALL.tar.xz","sig":"https://cdn.mullvad.net/browser/12.5/mullvad-browser-linux64-12.5_ALL.tar.xz.asc"}},"macos":{"ALL":{"binary":"https://cdn.mullvad.net/browser/12.5/MullvadBrowser-12.5-macos_ALL.dmg","sig":"https://cdn.mullvad.net/browser/12.5/MullvadBrowser-12.5-macos_ALL.dmg.asc"}},"win64":{"ALL":{"binary":"https://cdn.mullvad.net/browser/12.5/mullvadbrowser-install-win64-12.5_ALL.exe","sig":"https://cdn.mullvad.net/browser/12.5/mullvadbrowser-install-win64-12.5_ALL.exe.asc"}}},"tag":"tbb-12.5-build1","version":12.5}
\ No newline at end of file
+{"downloads":{"linux64":{"ALL":{"binary":"https://cdn.mullvad.net/browser/12.5/mullvad-browser-linux64-12.5_ALL.tar.xz","sig":"https://cdn.mullvad.net/browser/12.5/mullvad-browser-linux64-12.5_ALL.tar.xz.asc"}},"macos":{"ALL":{"binary":"https://cdn.mullvad.net/browser/12.5/MullvadBrowser-12.5-macos_ALL.dmg","sig":"https://cdn.mullvad.net/browser/12.5/MullvadBrowser-12.5-macos_ALL.dmg.asc"}},"win64":{"ALL":{"binary":"https://cdn.mullvad.net/browser/12.5/mullvadbrowser-install-win64-12.5_ALL.exe","sig":"https://cdn.mullvad.net/browser/12.5/mullvadbrowser-install-win64-12.5_ALL.exe.asc"}}},"tag":"tbb-12.5-build1","version":"12.5"}
\ No newline at end of file