Remove unnecessary testing and documentation

Signed-off-by: Waleed Elmelegy <waleed.elmelegy@arm.com>
diff --git a/library/bignum_core.h b/library/bignum_core.h
index bebd810..b32d607 100644
--- a/library/bignum_core.h
+++ b/library/bignum_core.h
@@ -377,7 +377,7 @@
  * either otherwise.
  *
  * This function operates in constant time with respect to the values
- * of \p X and \p A and \p B.
+ * of \p A and \p B.
  *
  * \param[out] X    The result of the subtraction.
  * \param[in] A     Little-endian presentation of left operand.