Fix docs grammar

Signed-off-by: Dave Rodgman <dave.rodgman@arm.com>
diff --git a/library/constant_time_internal.h b/library/constant_time_internal.h
index 959fbf9..5879e47 100644
--- a/library/constant_time_internal.h
+++ b/library/constant_time_internal.h
@@ -65,9 +65,9 @@
  *
  * For Arm (32-bit, 64-bit and Thumb), x86 and x86-64, assembly implementations
  * are used to ensure that the generated code is constant time. For other
- * architectures, a plain C fallback designed to yield constant-time code (this
- * has been observed to be constant-time on latest gcc, clang and MSVC as of
- * May 2023).
+ * architectures, it uses a plain C fallback designed to yield constant-time code
+ * (this has been observed to be constant-time on latest gcc, clang and MSVC
+ * as of May 2023).
  */
 
 #if (SIZE_MAX > 0xffffffffffffffffULL)