Add missing quotation mark

Closes gh-1181

src/asciidoc/core-validation.adoc

@@ -136,7 +136,7 @@ and use it like so:
 			}
 			if (!addressValidator.supports(Address.class)) {
 				throw new IllegalArgumentException("The supplied [Validator] must " +
-					support the validation of [Address] instances.");
+					"support the validation of [Address] instances.");
 			}
 			this.addressValidator = addressValidator;
 		}