Resolve namespace clash with latest tlm_adjoint

Author: jrmaddison

fenics_ice/backend.py

@@ -16,3 +16,5 @@ def _Vector_inner(self, /, other):
 _Vector__inner_orig = cpp_PETScVector.inner
 cpp_PETScVector.inner = _Vector_inner
 del _Vector_inner, cpp_PETScVector
+
+from fenics import Vector