Stop stylizing PEP **518**

This is a slightly cleaner presentation style.

Author: pradyunsg

src/pip/_internal/exceptions.py

@@ -188,7 +188,7 @@ def __init__(self, *, package: str) -> None:
                 "The [build-system] table is missing the mandatory `requires` key."
             ),
             note_stmt="This is an issue with the package mentioned above, not pip.",
-            hint_stmt="See PEP 518 for the detailed specification.",
+            hint_stmt=Text("See PEP 518 for the detailed specification."),
         )
 
 
@@ -205,7 +205,7 @@ def __init__(self, *, package: str, reason: str) -> None:
                 f"pyproject.toml.\n{reason}"
             ),
             note_stmt="This is an issue with the package mentioned above, not pip.",
-            hint_stmt="See PEP 518 for the detailed specification.",
+            hint_stmt=Text("See PEP 518 for the detailed specification."),
         )