CLOUDP-274724 - readinessProbe: use human readable timestamps instead

[nammn]

Summary:

Change usage of zap as described by the lib:

// You may change these by setting the appropriate fields in the returned
// object.
// For example, use the following to change the time encoding format:
//
//	cfg := zap.NewProductionEncoderConfig()
//	cfg.EncodeTime = zapcore.ISO8601TimeEncoder

[lsierant]

This is awesome!