Arm backend: Increased pytest timeout (pytorch#18631)

Increased the pytest timeout 1200s->1800s
due to timeout on tiny stable diffusion

Signed-off-by: Christoffer J.L <christoffer.johanssonlundqvist@arm.com>

Author: Christoffer-JL

backends/arm/requirements-arm-tosa.txt

@@ -9,4 +9,4 @@ tosa-adapter-model-explorer == 0.1.0
 ai-edge-model-explorer >= 0.1.16
 # NOTE: Will be removed when tosa-tools is installed via pypi
 pybind11 == 2.10.4
-pytest-timeout
+pytest-timeout == 2.4.0

backends/arm/test/pytest.ini

@@ -1,5 +1,5 @@
 [pytest]
-timeout = 1200
+timeout = 1800
 addopts = --strict-markers
 markers =
     slow: Tests that take long time