Use require_relative instead of $LOAD_PATH in gemspec

Author: ericproulx

CHANGELOG.md

@@ -3,6 +3,7 @@
 #### Features
 
 * [#2572](https://github.com/ruby-grape/grape/pull/2572): Drop support ruby 2.7 and active_support 6.1 - [@ericproulx](https://github.com/ericproulx).
+* Use `require_relative` instead of `$LOAD_PATH` in gemspec - [@ericproulx](https://github.com/ericproulx).
 * [#2573](https://github.com/ruby-grape/grape/pull/2573): Clean up deprecated code - [@ericproulx](https://github.com/ericproulx).
 * [#2575](https://github.com/ruby-grape/grape/pull/2575): Refactor Api description class - [@ericproulx](https://github.com/ericproulx).
 * [#2577](https://github.com/ruby-grape/grape/pull/2577): Deprecate `return` in endpoint execution - [@ericproulx](https://github.com/ericproulx).

grape.gemspec

@@ -1,7 +1,6 @@
 # frozen_string_literal: true
 
-$LOAD_PATH.unshift File.expand_path('lib', __dir__)
-require 'grape/version'
+require_relative 'lib/grape/version'
 
 Gem::Specification.new do |s|
   s.name        = 'grape'