protobuf: 29.3 -> 30.0

Diff: https://github.com/protocolbuffers/protobuf/compare/v29.3...v30.0

Changelog:
https://github.com/protocolbuffers/protobuf/releases/tag/v30.0

pkgs/top-level/all-packages.nix

@@ -10947,7 +10947,7 @@ with pkgs;
 
   prospector = callPackage ../development/tools/prospector { };
 
-  protobuf = protobuf_29;
+  protobuf = protobuf_30;
 
   inherit
     ({

pkgs/top-level/python-packages.nix

@@ -11391,7 +11391,7 @@ self: super: with self; {
   proto-plus = callPackage ../development/python-modules/proto-plus { };
 
   # If a protobuf upgrade causes many Python packages to fail, please pin it here to the previous version.
-  protobuf = protobuf5;
+  protobuf = protobuf6;
 
   protobuf3-to-dict = callPackage ../development/python-modules/protobuf3-to-dict { };
 
@@ -11401,13 +11401,13 @@ self: super: with self; {
   };
 
   # Protobuf 5.x
-  protobuf5 = callPackage ../development/python-modules/protobuf/default.nix {
-    inherit (pkgs.__splicedPackages) protobuf;
+  protobuf5 = callPackage ../development/python-modules/protobuf/5.nix {
+    protobuf = pkgs.__splicedPackages.protobuf_29;
   };
 
   # Protobuf 6.x
   protobuf6 = callPackage ../development/python-modules/protobuf/6.nix {
-    inherit (pkgs.__splicedPackages) protobuf_30;
+    inherit (pkgs.__splicedPackages) protobuf;
   };
 
   proton-client = callPackage ../development/python-modules/proton-client { };