gnu: python-pytest-7.1: Deprecate package.

The source was adjusted using the following command:

   $ git grep -rl python-pytest-7.1 |
     xargs sed -i 's/python-pytest-7.1/python-pytest/g'

* gnu/packages/check.scm (python-pytest-7.1): Delete variable.

gnu/packages/python-crypto.scm

@@ -521,7 +521,7 @@ is used by the Requests library to verify HTTPS requests.")
            python-hypothesis
            python-iso8601
            python-pretend
-           python-pytest-7.1            ;for subtests
+           python-pytest                ;for subtests
            python-pytest-benchmark
            python-pytest-subtests))
     (inputs (list python-cryptography-rust))