Fix generate_sensitivity_code=False for event sensitivity functions (#3044)

With `generate_sensitivity_code=False`, amici still generated some unnecessary event sensivity functions. This is fixed here.

Author: dweindl

python/sdist/amici/exporters/sundials/cxx_functions.py

@@ -434,7 +434,7 @@ def var_in_signature(self, varname: str, ode: bool = True) -> bool:
     func_name
     for func_name, func_info in functions.items()
     if "const int ip" in func_info.arguments()
-]
+] + ["deltaxB", "dzdx", "drzdx"]
 
 #: list of sparse sensitivity functions
 sparse_sensi_functions = [
@@ -454,6 +454,7 @@ def var_in_signature(self, varname: str, ode: bool = True) -> bool:
 ]
 
 #: list of event sensitivity functions
+#  (really only those that take `ie` and `ip` as arguments)
 event_sensi_functions = [
     func_name
     for func_name, func_info in functions.items()