CustomLineHeightSpan: Increase the readability (#42592)

Summary:
Increase the readability of `CustomLineHeightSpan` by making the logic less stateful.

This is a minor improvement in the context of my multi-PR work on https://github.com/react-native-community/discussions-and-proposals/issues/695.

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[INTERNAL] [CHANGED] - Increase the readability of `CustomLineHeightSpan`

Pull Request resolved: https://github.com/facebook/react-native/pull/42592

Test Plan:
- Prove the equivalence of the old and the new logic
- Test that the behavior of `lineHeight` doesn't change

Reviewed By: NickGerleman

Differential Revision: D53028467

Pulled By: mdvacca

fbshipit-source-id: d533bb77c8e10c29d8f2acc8cc39565d0013b03b

packages/react-native/ReactAndroid/src/main/java/com/facebook/react/views/text/CustomLineHeightSpan.java

@@ -54,10 +54,13 @@ public class CustomLineHeightSpan implements LineHeightSpan, ReactSpan {
 
       // Round up for the negative values and down for the positive values  (arbitrary choice)
       // So that bottom - top equals additional even if it's an odd number.
-      fm.top -= Math.ceil(additional / 2.0f);
-      fm.bottom += Math.floor(additional / 2.0f);
-      fm.ascent = fm.top;
-      fm.descent = fm.bottom;
+      final int top = (int) (fm.top - Math.ceil(additional / 2.0f));
+      final int bottom = (int) (fm.bottom + Math.floor(additional / 2.0f));
+
+      fm.top = top;
+      fm.ascent = top;
+      fm.descent = bottom;
+      fm.bottom = bottom;
     }
   }
 }