Change use_fractional_gates default to False (#1755)

* set default to false

* release note

---------

Co-authored-by: Kevin Tian <kevin.tian@ibm.com>

qiskit_ibm_runtime/qiskit_runtime_service.py

@@ -458,7 +458,7 @@ def backends(
         dynamic_circuits: Optional[bool] = None,
         filters: Optional[Callable[[List["ibm_backend.IBMBackend"]], bool]] = None,
         *,
-        use_fractional_gates: Optional[bool] = True,
+        use_fractional_gates: bool = False,
         **kwargs: Any,
     ) -> List["ibm_backend.IBMBackend"]:
         """Return all backends accessible via this account, subject to optional filtering.
@@ -735,7 +735,7 @@ def backend(
         self,
         name: str = None,
         instance: Optional[str] = None,
-        use_fractional_gates: bool = True,
+        use_fractional_gates: bool = False,
     ) -> Backend:
         """Return a single backend matching the specified filtering.
 

release-notes/unreleased/1755.bug.rst

@@ -0,0 +1 @@
+Disallowing fractional gates by default, so backend target would not exclude control flow.