Changing the default value to have tracing without performance out of the box

Author: antonpirker

sentry_sdk/consts.py

@@ -511,7 +511,7 @@ def __init__(
         debug=None,  # type: Optional[bool]
         attach_stacktrace=False,  # type: bool
         ca_certs=None,  # type: Optional[str]
-        traces_sample_rate=None,  # type: Optional[float]
+        traces_sample_rate=0,  # type: Optional[float]
         traces_sampler=None,  # type: Optional[TracesSampler]
         profiles_sample_rate=None,  # type: Optional[float]
         profiles_sampler=None,  # type: Optional[TracesSampler]