Update spec/Appendix C -- Built-in Definitions.md

Co-authored-by: Benjie <[email protected]>

Author: martinbonnin

spec/Appendix C -- Built-in Definitions.md

@@ -72,7 +72,7 @@ directive @deprecated(
   The reason for the deprecation.
   """
   reason: String! = "No longer supported"
-) on FIELD_DEFINITION | ARGUMENT_DEFINITION | ENUM_VALUE | INPUT_FIELD_DEFINITION
+) on FIELD_DEFINITION | ARGUMENT_DEFINITION | INPUT_FIELD_DEFINITION | ENUM_VALUE
 
 """
 Exposes a URL that specifies the behavior of this scalar.