Allow finding Python in other locations

Although a lot of Linux OS's provide Python in /usr/bin that is not always the case
and outside of Linux that is not the case.

registry/apiconventions.py

@@ -1,4 +1,4 @@
-#!/usr/bin/python3 -i
+#!/usr/bin/env python3 -i
 #
 # Copyright 2021-2023 The Khronos Group Inc.
 # SPDX-License-Identifier: Apache-2.0

registry/cgenerator.py

@@ -1,4 +1,4 @@
-#!/usr/bin/python3 -i
+#!/usr/bin/env python3 -i
 #
 # Copyright 2013-2023 The Khronos Group Inc.
 #

registry/generator.py

@@ -1,4 +1,4 @@
-#!/usr/bin/python3 -i
+#!/usr/bin/env python3 -i
 #
 # Copyright 2013-2023 The Khronos Group Inc.
 #

registry/genvk.py

@@ -1,4 +1,4 @@
-#!/usr/bin/python3
+#!/usr/bin/env python3
 #
 # Copyright 2013-2023 The Khronos Group Inc.
 #

registry/parse_dependency.py

@@ -1,4 +1,4 @@
-#!/usr/bin/python3
+#!/usr/bin/env python3
 
 # Copyright 2022-2023 The Khronos Group Inc.
 # Copyright 2003-2019 Paul McGuire

registry/reg.py

@@ -1,4 +1,4 @@
-#!/usr/bin/python3 -i
+#!/usr/bin/env python3 -i
 #
 # Copyright 2013-2023 The Khronos Group Inc.
 #

registry/spec_tools/conventions.py

@@ -1,4 +1,4 @@
-#!/usr/bin/python3 -i
+#!/usr/bin/env python3 -i
 #
 # Copyright 2013-2023 The Khronos Group Inc.
 #

registry/stripAPI.py

@@ -1,4 +1,4 @@
-#!/usr/bin/python3
+#!/usr/bin/env python3
 #
 # Copyright 2023 The Khronos Group Inc.
 # SPDX-License-Identifier: Apache-2.0

registry/vkconventions.py

@@ -1,4 +1,4 @@
-#!/usr/bin/python3 -i
+#!/usr/bin/env python3 -i
 #
 # Copyright 2013-2023 The Khronos Group Inc.
 #