Fix lint errors and update yarn_lockfile_updater test

- Remove unnecessary rubocop:disable/enable Metrics/PerceivedComplexity
- Convert if block to modifier style per Style/IfUnlessModifier
- Update yarn_lockfile_updater_spec to expect MisconfiguredTooling
  (with the FF removed, single-dep scenarios no longer raise
  "Expected content to change!" — the yarn updater now correctly
  detects the misconfigured .yarnrc.yml)

Co-authored-by: pavera <660677+pavera@users.noreply.github.com>

Author: Copilot

bun/lib/dependabot/bun/file_updater/package_json_updater.rb

@@ -41,8 +41,6 @@ def updated_package_json
         sig { returns(T::Array[Dependabot::Dependency]) }
         attr_reader :dependencies
 
-        # rubocop:disable Metrics/PerceivedComplexity
-
         sig { returns(T.nilable(String)) }
         def updated_package_json_content
           # checks if we are updating single dependency in package.json
@@ -65,9 +63,7 @@ def updated_package_json_content
               # The other dependency is not present in package.json so we don't have to update it — this is
               # most likely a transitive dependency which only needs an update in the lockfile. We avoid
               # throwing an exception and let the update continue.
-              if content == new_content && unique_deps_count > 1
-                raise "Expected content to change!"
-              end
+              raise "Expected content to change!" if content == new_content && unique_deps_count > 1
 
               content = new_content
             end
@@ -86,7 +82,6 @@ def updated_package_json_content
             content
           end
         end
-        # rubocop:enable Metrics/PerceivedComplexity
         sig do
           params(
             dependency: Dependabot::Dependency,

npm_and_yarn/lib/dependabot/npm_and_yarn/file_updater/package_json_updater.rb

@@ -41,8 +41,6 @@ def updated_package_json
         sig { returns(T::Array[Dependabot::Dependency]) }
         attr_reader :dependencies
 
-        # rubocop:disable Metrics/PerceivedComplexity
-
         sig { returns(T.nilable(String)) }
         def updated_package_json_content
           # checks if we are updating single dependency in package.json
@@ -65,9 +63,7 @@ def updated_package_json_content
               # The other dependency is not present in package.json so we don't have to update it — this is
               # most likely a transitive dependency which only needs an update in the lockfile. We avoid
               # throwing an exception and let the update continue.
-              if content == new_content && unique_deps_count > 1
-                raise "Expected content to change!"
-              end
+              raise "Expected content to change!" if content == new_content && unique_deps_count > 1
 
               content = new_content
             end
@@ -86,7 +82,6 @@ def updated_package_json_content
             content
           end
         end
-        # rubocop:enable Metrics/PerceivedComplexity
         sig do
           params(
             dependency: Dependabot::Dependency,

npm_and_yarn/spec/dependabot/npm_and_yarn/file_updater/yarn_lockfile_updater_spec.rb

@@ -142,7 +142,7 @@
 
       it "raises a helpful error" do
         expect { updated_yarn_lock_content }
-          .to raise_error("Expected content to change!")
+          .to raise_error(Dependabot::MisconfiguredTooling)
       end
     end