minor #16862 [Form] Fix constants (OskarStark)

This PR was merged into the 5.4 branch.

Discussion
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[Form] Fix constants

See down in the file
```
* ``\NumberFormatter::ROUND_HALFUP`` Round towards the
  "nearest neighbor". If both neighbors are equidistant, round up. It rounds
  ``2.5`` to ``3``, ``1.6`` and ``1.5`` to ``2`` and ``1.4`` to ``1``.
```

Commits
-------

f7075dc [Form][NumberType] Fix constants

Author: javiereguiluz

reference/forms/types/options/rounding_mode.rst.inc

@@ -2,13 +2,13 @@ rounding_mode
 ~~~~~~~~~~~~~
 
 **type**: ``integer`` **default**: ``\NumberFormatter::ROUND_DOWN`` for ``IntegerType``
-and ``\NumberFormatter::ROUND_HALF_UP`` for ``MoneyType`` and ``NumberType``
+and ``\NumberFormatter::ROUND_HALFUP`` for ``MoneyType`` and ``NumberType``
 
 * IntegerType
 **default**: ``\NumberFormatter::ROUND_DOWN``
 
 * MoneyType and NumberType
-**default**: ``\NumberFormatter::ROUND_HALF_UP``
+**default**: ``\NumberFormatter::ROUND_HALFUP``
 
 
 If a submitted number needs to be rounded (based on the `scale`_ option), you