Jump on last major release as a minimal requirement

Makes sense long term, one can prefer older releases when stuck with
ancient proto versions.

Author: mostlyobvious

protobuf_nested_struct.gemspec

@@ -29,5 +29,5 @@ Gem::Specification.new do |spec|
 
   spec.required_ruby_version = ">= 2.7"
 
-  spec.add_dependency "google-protobuf", ">= 3.25.7"
+  spec.add_dependency "google-protobuf", ">= 4.26.0"
 end