Update sqlite3 dependency from ~> 1.3.6 to >= 1.4 for Rails 7+ compatibility

Rails 7.0+ requires sqlite3 >= 1.4. The previous constraint of ~> 1.3.6 was
causing bundler to activate sqlite3-1.3.13 which is incompatible with Rails 7.2+.

Error message: "can't activate sqlite3 (>= 1.4), already activated sqlite3-1.3.13"

Changed: s.add_development_dependency "sqlite3", "~> 1.3.6"
To: s.add_development_dependency "sqlite3", ">= 1.4"

Reference: https://guides.rubyonrails.org/7_0_release_notes.html
The sqlite3 1.4+ series includes performance improvements and better Ruby 3+ compatibility.

Author: chrisarcand

vault.gemspec

@@ -31,7 +31,7 @@ Gem::Specification.new do |s|
   s.add_development_dependency "pry-byebug"
   s.add_development_dependency "rake",    "~> 12.3.3"
   s.add_development_dependency "rspec",   "~> 3.2"
-  s.add_development_dependency "sqlite3", "~> 1.3.6"
+  s.add_development_dependency "sqlite3", ">= 1.4"
   # ostruct will be removed from Ruby's default gems in 3.5.0
   # rake 12.3.3 depends on it but doesn't declare it explicitly
   s.add_development_dependency "ostruct"