Remove "thank you for testing" from the welcome message, closes #1036

This small piece of the welcome message could give off the impression
that ForgeGradle 7.0 is still incubating software. It is not.

Author: Jonathing

src/main/java/net/minecraftforge/gradle/internal/Constants.java

@@ -70,10 +70,7 @@ please see our MDKExamples repo (https://github.com/MinecraftForge/MDKExamples).
         static final String WELCOME_CONDITION = """
             This message will not display again until ForgeGradle 7.1 or the below file is
             deleted:
-            {}
-
-            Documentation will be coming at a later date. Thank you for testing
-            ForgeGradle 7!""";
+            {}""";
 
         // TODO [ForgeGradle][Magic] Rewrite this to be more informative as to what is actually happening.
         //      As of right now, this remains unused.