PERF: Replace isclose() comparison with explicit bounds

Rather than using isclose() we can directly compare against the
expected values using array indexing.

pymsis/msis.py

@@ -190,9 +190,8 @@ def run(
         )
 
     # The Fortran code puts 9.9e-38 in as NaN
-    # Have to make sure this doesn't overlap 0 due to really small values
-    # so atol should be less than the comparison value
-    output[np.isclose(output, 9.9e-38, atol=1e-38)] = np.nan
+    # or 9.99e-38, or 9.999e-38, so lets just bound the 9s
+    output[(output >= 9.9e-38) & (output < 1e-37)] = np.nan  # noqa: PLR2004
 
     return output.reshape(*input_shape, 11)