[3.13] Replace strict_concatenate = True with extra_checks = True (pythonGH-126391) (python#129286)

Replace `strict_concatenate = True` with `extra_checks = True` (pythonGH-126391)
(cherry picked from commit cc4f0a2)

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

Author: miss-islington

Tools/build/mypy.ini

@@ -8,6 +8,6 @@ python_version = 3.10
 
 # ...And be strict:
 strict = True
-strict_concatenate = True
+extra_checks = True
 enable_error_code = ignore-without-code,redundant-expr,truthy-bool,possibly-undefined
 warn_unreachable = True

Tools/cases_generator/mypy.ini

@@ -8,7 +8,7 @@ python_version = 3.10
 
 # ...And be strict:
 strict = True
-strict_concatenate = True
+extra_checks = True
 enable_error_code = ignore-without-code,redundant-expr,truthy-bool,possibly-undefined
 warn_unreachable = True
 allow_redefinition = True

Tools/clinic/mypy.ini

@@ -7,6 +7,6 @@ python_version = 3.10
 
 # and be strict!
 strict = True
-strict_concatenate = True
+extra_checks = True
 enable_error_code = ignore-without-code,redundant-expr,truthy-bool
 warn_unreachable = True