Remove unnecessary code

Unless using ruby 2.3 or older, or even of ruby 2.3 if a modern enough
bundler is used, the bundler gemspec should never have its `loaded_from`
attribute set to a missing file, so this whole hack shouldn't be
necessary.

.travis.yml

@@ -1,5 +1,4 @@
 rvm:
-  - jruby-9.0.5.0
   - jruby-9.1.17.0
   - jruby-9.2.0.0
 jdk:
@@ -36,8 +35,5 @@ notifications:
       - "%{repository} (%{branch}:%{commit} by %{author}): %{message} (%{build_url})"
 before_install:
   - git fetch --unshallow
-  - gem update --system 2.6.14
+  - gem update --system 3.2.17
   - gem --version
-  - rvm @global do gem uninstall bundler -a -x -I || true
-  - gem uninstall bundler -a -x -I || true
-  - gem install bundler -v '< 2'

lib/warbler/traits/bundler.rb

@@ -38,22 +38,6 @@ def add_bundler_gems; require 'bundler'
 
         bundler_specs.each do |spec|
           spec = to_spec(spec)
-          # Bundler HAX -- fixup bad #loaded_from attribute in fake
-          # bundler gemspec from bundler/source.rb
-          if spec.name == 'bundler'
-            full_gem_path = Pathname.new(spec.full_gem_path)
-            while ! full_gem_path.join('bundler.gemspec').exist?
-              full_gem_path = full_gem_path.dirname
-              # if at top of the path, meaning we cannot find bundler.gemspec, abort.
-              if full_gem_path.to_s =~ /^[\.\/]$/
-                warn("Unable to detect bundler spec under '#{spec.full_gem_path}'' and its sub-dirs")
-                exit
-              end
-            end
-
-            spec.loaded_from = full_gem_path.join('bundler.gemspec').to_s
-            spec.full_gem_path = full_gem_path.to_s
-          end
 
           case spec.source
           when ::Bundler::Source::Git