Don't use \ in f-string

Author: oscarbenjamin

src/protosym/simplecas/functions.py

@@ -82,7 +82,7 @@
 # ------------------------------------------------------------------------- #
 
 latex_add = PyOpN(lambda args: f'({" + ".join(args)})')
-latex_mul = PyOpN(lambda args: f"({' \\times '.join(args)})")
+latex_mul = PyOpN(lambda args: "(" + r" \times ".join(args) + ")")
 latex_pow = PyOp2(lambda b, e: f"{b}^{{{e}}}")
 latex_sin = PyOp1(lambda a: rf"\sin({a})")
 latex_cos = PyOp1(lambda a: rf"\cos({a})")