Removing deleted files from dist rule (#10141)

Makefile.am

@@ -119,7 +119,6 @@ csharp_EXTRA_DIST=                                                           \
   csharp/src/Google.Protobuf.Test/Collections/ProtobufEqualityComparersTest.cs \
   csharp/src/Google.Protobuf.Test/Collections/RepeatedFieldTest.cs           \
   csharp/src/Google.Protobuf.Test/Compatibility/PropertyInfoExtensionsTest.cs \
-  csharp/src/Google.Protobuf.Test/Compatibility/StreamExtensionsTest.cs      \
   csharp/src/Google.Protobuf.Test/Compatibility/TypeExtensionsTest.cs        \
   csharp/src/Google.Protobuf.Test/DeprecatedMemberTest.cs                    \
   csharp/src/Google.Protobuf.Test/EqualityTester.cs                          \
@@ -185,14 +184,11 @@ csharp_EXTRA_DIST=                                                           \
   csharp/src/Google.Protobuf/Collections/Lists.cs                            \
   csharp/src/Google.Protobuf/Collections/MapField.cs                         \
   csharp/src/Google.Protobuf/Collections/ProtobufEqualityComparers.cs        \
-  csharp/src/Google.Protobuf/Collections/ReadOnlyDictionary.cs               \
   csharp/src/Google.Protobuf/Collections/RepeatedField.cs                    \
   csharp/src/Google.Protobuf/Compatibility/DynamicallyAccessedMembersAttribute.cs \
   csharp/src/Google.Protobuf/Compatibility/DynamicallyAccessedMemberTypes.cs \
-  csharp/src/Google.Protobuf/Compatibility/MethodInfoExtensions.cs           \
   csharp/src/Google.Protobuf/Compatibility/PropertyInfoExtensions.cs         \
   csharp/src/Google.Protobuf/Compatibility/RequiresUnreferencedCodeAttribute.cs \
-  csharp/src/Google.Protobuf/Compatibility/StreamExtensions.cs               \
   csharp/src/Google.Protobuf/Compatibility/TypeExtensions.cs                 \
   csharp/src/Google.Protobuf/Compatibility/UnconditionalSuppressMessageAttribute.cs \
   csharp/src/Google.Protobuf/Extension.cs                                    \