Clarify error message for non `@runtime_checkable` decorated protocols (#178)

CHANGELOG.md

diff --git a/CHANGELOG.md b/CHANGELOG.md
index 74381f8..3a8bdde 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -1,3 +1,8 @@
+# Unreleased
+
+- Change deprecated `@runtime` to formal API `@runtime_checkable` in the error
+  message. Patch by Xuehai Pan.
+
 # Release 4.6.0 (May 22, 2023)
 
 - `typing_extensions` is now documented at

src/typing_extensions.py

diff --git a/src/typing_extensions.py b/src/typing_extensions.py
index 7866555..e2b2dc6 100644
--- a/src/typing_extensions.py
+++ b/src/typing_extensions.py
@@ -701,7 +701,7 @@
                     if _allow_reckless_class_checks():
                         return NotImplemented
                     raise TypeError("Instance and class checks can only be used with"
-                                    " @runtime protocols")
+                                    " @runtime_checkable protocols")
                 if not isinstance(other, type):
                     # Same error as for issubclass(1, int)
                     raise TypeError('issubclass() arg 1 must be a class')