glsl: remove execute bit and shebang from python tests

Just like the rest of the tree - these should be run either as part of
the build system check target, or at the very least with an explicitly
versioned python executable.

Fixes: db8cd8e367 ("glcpp/tests: Convert shell scripts to a python script")
Fixes: 97c28cb082 ("glsl/tests: Convert optimization-test.sh to pure python")
Fixes: 3b52d29227 ("glsl/tests: reimplement warnings-test in python")
Signed-off-by: Emil Velikov <emil.velikov@collabora.com>
Reviewed-by: Dylan Baker <dylan@pnwbakers.com>
Reviewed-by: Eric Engestrom <eric.engestrom@intel.com>
(cherry picked from commit 48820ed8da)
[Andres Gomez: resolve trivial conflicts]
Signed-off-by: Andres Gomez <agomez@igalia.com>

Conflicts:
	src/compiler/glsl/tests/optimization_test.py

src/compiler/glsl/glcpp/tests/glcpp_test.py

@@ -1,4 +1,3 @@
-#!/usr/bin/env python2
 # encoding=utf-8
 # Copyright © 2018 Intel Corporation
 

src/compiler/glsl/tests/optimization_test.py

@@ -1,4 +1,3 @@
-#!/usr/bin/env python2
 # encoding=utf-8
 # Copyright © 2018 Intel Corporation
 

src/compiler/glsl/tests/warnings_test.py

@@ -1,4 +1,3 @@
-#!/usr/bin/env python
 # encoding=utf-8
 # Copyright © 2017 Intel Corporation