Revert "Update function-pointer.md for stabilization of `extended_varargs_abi_support`"

src/types/function-pointer.md

diff --git a/src/types/function-pointer.md b/src/types/function-pointer.md
index 243e8e6..640b3fc 100644
--- a/src/types/function-pointer.md
+++ b/src/types/function-pointer.md
@@ -52,14 +52,7 @@
 
 r[type.fn-pointer.constraint-variadic]
 Variadic parameters can only be specified with [`extern`] function types with
-these calling conventions:
-* `C`
-* `cdecl`
-* `system`
-* `aapcs`
-* `sysv64`
-* `win64`
-* `efiapi`
+the `"C"` or `"cdecl"` calling convention.
 
 r[type.fn-pointer.attributes]
 ## Attributes on function pointer parameters