Review feedback from @gregtatcam: STAmount

- Fix a couple of typos.
- Make fewer unneeded copies in roundToScale.

include/xrpl/protocol/STAmount.h

@@ -701,7 +701,7 @@ getRate(STAmount const& offerOut, STAmount const& offerIn);
  */
 STAmount
 roundToScale(
-    STAmount value,
+    STAmount const& value,
     std::int32_t scale,
     Number::rounding_mode rounding = Number::getround());
 
@@ -729,7 +729,7 @@ roundToAsset(
     STAmount const ret{asset, value};
     if (ret.integral())
         return ret;
-    // Not that the ctor will round integral types (XRP, MPT) via canonicalize,
+    // Note that the ctor will round integral types (XRP, MPT) via canonicalize,
     // so no extra work is needed for those.
     return roundToScale(ret, scale);
 }