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))