Relax activesupport dependency version restriction

**Changes:**
- Removed the upper boundary `< 8.1` for `activesupport` dependency in `featury.gemspec` and `Gemfile.lock`.
- Ensures compatibility with future major versions of `activesupport` while maintaining the minimum requirement of `>= 5.1`.

Author: afuno

Gemfile.lock

@@ -2,7 +2,7 @@ PATH
   remote: .
   specs:
     featury (1.0.0.rc26)
-      activesupport (>= 5.1, < 8.1)
+      activesupport (>= 5.1)
       i18n (>= 1.14)
       servactory (>= 2.16)
       zeitwerk (>= 2.6)

featury.gemspec

@@ -29,7 +29,7 @@ Gem::Specification.new do |spec|
 
   spec.required_ruby_version = Gem::Requirement.new(">= 3.2")
 
-  spec.add_dependency "activesupport", ">= 5.1", "< 8.1"
+  spec.add_dependency "activesupport", ">= 5.1"
   spec.add_dependency "i18n", ">= 1.14"
   spec.add_dependency "servactory", ">= 2.16"
   spec.add_dependency "zeitwerk", ">= 2.6"