Drop 32-bit platforms from the set of native precompiled gems.

[flavorjones]

Summary

Stop shipping 32-bit precompiled packages.

Rationale

An RFC that proposed this has been open for a year and there have been no objections.

#3081

Here's the historical downloads, including % of total downloads, for the 32-bit platforms during the "precompiled native gem" era:

- v1.11 / 2021-01-04:
  - x86-mingw32:         26,480 ( 0.04%)
  - x86-linux:           21,335 ( 0.03%)
- v1.12 / 2021-08-02:
  - x86-mingw32:         14,683 ( 0.03%)
  - x86-linux:           12,712 ( 0.02%)
- v1.13 / 2022-01-06:
  - x86-mingw32:         19,824 ( 0.02%)
  - x86-linux:           14,484 ( 0.01%)
- v1.14 / 2023-01-12:
  - x86-mingw32:          6,493 ( 0.01%)
  - x86-linux:            5,384 ( 0.01%)
- v1.15 / 2023-05-15:
  - x86-mingw32:          9,930 ( 0.01%)
  - x86-linux:            5,137 ( 0.01%)
- v1.16 / 2023-12-27:
  - x86-linux:           13,793 ( 0.02%)
  - x86-mingw32:         11,928 ( 0.01%)

These numbers are low enough that I'm pretty sure it's almost entirely mirrors and bots downloading them.

Although the effort to maintain these precompiled native gems is relatively low, there don't appear to be any actual users.