imgtool: Bump cryptography library version

Update requirements.txt to fix failing CI jobs due to
missing PrivateKeyType and PublicKeyType which are available
in cryptography library since version 40.0.0

Signed-off-by: Rustam Ismayilov <[email protected]>
Change-Id: I63552966051a19dc33d5c53b499d216bcfdcf89b

Author: rustammendel

scripts/requirements.txt

@@ -1,4 +1,4 @@
-cryptography>=2.6
+cryptography>=40.0.0
 intelhex
 click
 cbor2

scripts/setup.py

@@ -1,6 +1,7 @@
 # SPDX-License-Identifier: Apache-2.0
 
 import setuptools
+
 from imgtool import imgtool_version
 
 setuptools.setup(
@@ -14,7 +15,7 @@
     packages=setuptools.find_packages(),
     python_requires='>=3.6',
     install_requires=[
-        'cryptography>=2.4.2',
+        'cryptography>=40.0.0',
         'intelhex>=2.2.1',
         'click',
         'cbor2',