Use a looser tolerance on pitch for HexGrid roughly equal check

We don't need a super strict check to make sure the grids are roughly
equal. The ideal of the method is to check that one index location in
one grid would be in approximately the same spatial location in the
other grid. Otherwise we can't accurately rotate the position within the
grid.

This problem came up in some shuffling work where two assemblies had
ever so slightly different pitches, on the order of hundreths of a
percent. The strict `other.pitch == self.pitch` failed even though, for
the purposes of this method, the two grids are "roughly equal"

armi/reactor/grids/hexagonal.py

@@ -12,7 +12,7 @@
 # See the License for the specific language governing permissions and
 # limitations under the License.
 from collections import deque
-from math import sqrt
+from math import isclose, sqrt
 from typing import List, Optional, Tuple
 
 import numpy as np
@@ -639,6 +639,6 @@ def _roughlyEqual(self, other) -> bool:
             return True
         return (
             isinstance(other, HexGrid)
-            and other.pitch == self.pitch
+            and isclose(self.pitch, other.pitch, rel_tol=1e-4)
             and other.cornersUp == self.cornersUp
         )