Corrected the generated version and added a unit test for it (#1894)

Author: dlemstra

tests/Magick.NET.Tests/MagickNETTests/TheVersionProperty.cs

@@ -45,5 +45,11 @@ public void ShouldContainTheCorrectFramework()
             Assert.Contains("net8.0", MagickNET.Version);
 #endif
         }
+
+        [Fact]
+        public void ShouldContainTheCorrectVersion()
+        {
+            Assert.Contains("14.8.1", MagickNET.Version);
+        }
     }
 }

tools/Magick.NET.SourceGenerator/AssemblyInfo/MagickVersionGenerator.cs

@@ -29,7 +29,7 @@ private string GetVersion(GeneratorAttributeSyntaxContext context)
             .ConstructorArguments.FirstOrDefault().Value?.ToString();
 
         var version = assemblyAttributes
-            .Single(attribute => attribute.AttributeClass?.ToDisplayString() == typeof(AssemblyVersionAttribute).FullName)
+            .Single(attribute => attribute.AttributeClass?.ToDisplayString() == typeof(AssemblyFileVersionAttribute).FullName)
             .ConstructorArguments.FirstOrDefault().Value?.ToString();
 
         if (title is null || version is null)