[PSM Interop] Fix PyYAML Cython build / Upgrade PyYAML to 6.0 (#33745)

Upgrades PyYAML from 5.4.1 to 6.0 to address cython build issue:
https://github.com/yaml/pyyaml/issues/601.

Changelog: https://github.com/yaml/pyyaml/blob/master/CHANGES

tools/run_tests/xds_k8s_test_driver/.gitignore

@@ -1,4 +1,5 @@
 config/local-*.cfg
 src/proto
 venv/
+venv-*/
 out/

tools/run_tests/xds_k8s_test_driver/requirements.lock

@@ -1,5 +1,5 @@
 Mako==1.2.4
-PyYAML==5.4.1
+PyYAML==6.0
 absl-py==0.15.0
 google-api-python-client==1.12.11
 google-cloud-secret-manager==2.15.1

tools/run_tests/xds_k8s_test_driver/requirements.txt

@@ -1,5 +1,5 @@
 Mako~=1.1
-PyYAML~=5.3
+PyYAML~=6.0
 absl-py~=0.11
 google-api-python-client~=1.12
 google-cloud-secret-manager~=2.1