set the rule as opt-in

Author: AhmedZaghloul19

Source/SwiftLintBuiltInRules/Rules/Style/MultipleVariableDeclarationRule.swift

@@ -1,6 +1,6 @@
 import SwiftSyntax
 
-@SwiftSyntaxRule
+@SwiftSyntaxRule(optIn: true)
 struct MultipleVariableDeclarationRule: Rule {
     var configuration = SeverityConfiguration<Self>(.warning)
 

Tests/GeneratedTests/GeneratedTests.swift

@@ -715,6 +715,12 @@ final class MultipleClosuresWithTrailingClosureRuleGeneratedTests: SwiftLintTest
     }
 }
 
+final class MultipleVariableDeclarationRuleGeneratedTests: SwiftLintTestCase {
+    func testWithDefaultConfiguration() {
+        verifyRule(MultipleVariableDeclarationRule.description)
+    }
+}
+
 final class NSLocalizedStringKeyRuleGeneratedTests: SwiftLintTestCase {
     func testWithDefaultConfiguration() {
         verifyRule(NSLocalizedStringKeyRule.description)
@@ -1464,9 +1470,3 @@ final class YodaConditionRuleGeneratedTests: SwiftLintTestCase {
         verifyRule(YodaConditionRule.description)
     }
 }
-
-final class MultipleVariableDeclarationRuleGeneratedTests: SwiftLintTestCase {
-    func testWithDefaultConfiguration() {
-        verifyRule(MultipleVariableDeclarationRule.description)
-    }
-}

Tests/IntegrationTests/default_rule_configurations.yml

@@ -567,7 +567,7 @@ multiple_closures_with_trailing_closure:
 multiple_variable_declaration:
   severity: warning
   meta:
-    opt-in: false
+    opt-in: true
 nesting:
   type_level:
     warning: 1