fix ImageMagickComparer error text (#744)

Author: SimonCropp

src/Directory.Build.props

@@ -2,7 +2,7 @@
 <Project>
   <PropertyGroup>
     <NoWarn>CS1591;CS0649;NU1608;NU1109</NoWarn>
-    <Version>3.7.3</Version>
+    <Version>3.7.4</Version>
     <AssemblyVersion>1.0.0</AssemblyVersion>
     <ImplicitUsings>enable</ImplicitUsings>
     <LangVersion>preview</LangVersion>

src/Tests/Samples.VerifyPdf#00.verified.png

@@ -5,5 +5,5 @@ diff(0.03612685510802296) > threshold(0.0001).
 If this difference is acceptable, use:
 
  * Globally: VerifyImageMagick.RegisterComparers(0.04);
- * For one test: Verifier.VerifyFile("file.jpg").RegisterComparers(0.04);
+ * For one test: Verifier.VerifyFile("file.jpg").ImageMagickComparer(0.04);
 }

src/Tests/Samples.VerifyPdf#01.verified.png

@@ -129,7 +129,7 @@ static Task<CompareResult> Compare(double threshold, ErrorMetric metric, IMagick
                  If this difference is acceptable, use:
 
                   * Globally: VerifyImageMagick.RegisterComparers({round});
-                  * For one test: Verifier.VerifyFile("file.jpg").RegisterComparers({round});
+                  * For one test: Verifier.VerifyFile("file.jpg").ImageMagickComparer({round});
                  """));
     }