Pin rsa version to 3.1.4.
Pin rsa version to 3.1.4.

PiperOrigin-RevId: 315798209

GoogleCloudPlatform/PerfKitBenchmarker,GoogleCloudPlatform/PerfKitBenchmarker,GoogleCloudPlatform/PerfKitBenchmarker,GoogleCloudPlatform/PerfKitBenchmarker