Revert "protobuf: 32.1 -> 33.0"

This reverts commit 1ab437d856.

This breaks the use of e.g onnxruntime and tensorflow in the same Python
process, since they now introduce the default systemd protobuf (33) and
the statically linked protobuf in tensorflow (32.1).

This breakage is visible in the frigate tests, which segfault due to this
misalignment.

pkgs/top-level/all-packages.nix

@@ -8240,7 +8240,7 @@ with pkgs;
 
   prospector = callPackage ../development/tools/prospector { };
 
-  protobuf = protobuf_33;
+  protobuf = protobuf_32;
 
   inherit
     ({