Clarify why quaternions are used

docs/api/en/math/Quaternion.html

@@ -12,9 +12,8 @@
 
 		<p class="desc">
 			Implementation of a [link:http://en.wikipedia.org/wiki/Quaternion quaternion].
-			This is used for [link:https://en.wikipedia.org/wiki/Quaternions_and_spatial_rotation rotating things]
-			without encountering the dreaded
-			[link:http://en.wikipedia.org/wiki/Gimbal_lock gimbal lock] issue, amongst other
+			This is used for [link:https://en.wikipedia.org/wiki/Quaternions_and_spatial_rotation describing rotations]
+			more concisely compared to 3x3 matrices, amongst other
 			advantages.
 		</p>
 

docs/api/zh/math/Quaternion.html

@@ -12,9 +12,8 @@
 
 		<p class="desc">
 			Implementation of a [link:http://en.wikipedia.org/wiki/Quaternion quaternion].
-			This is used for [link:https://en.wikipedia.org/wiki/Quaternions_and_spatial_rotation rotating things]
-			without encountering the dreaded
-			[link:http://en.wikipedia.org/wiki/Gimbal_lock gimbal lock] issue, amongst other
+			This is used for [link:https://en.wikipedia.org/wiki/Quaternions_and_spatial_rotation describing rotations]
+			more concisely compared to 3x3 matrices, amongst other
 			advantages.
 		</p>