Use 64bit containers to build 32bit Windows Tor Browser

Currently we use a 32bit container to build the Windows 32bit Tor Browser. I think we could do it from a 64bit container.

Doing that would:

reduce the number of container images we generate and store, as we would then use the same ones for the 32bit and 64bit builds
avoid potential memory limitations in the future (similarly to legacy/trac#26323 (moved))

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