Clarify that resize doesn't initialize memory

Some users might expect resize() to initialize added elements to zero. This clarifies that it is not the case.

doc/classes/PoolByteArray.xml

@@ -112,6 +112,7 @@
 			<argument index="0" name="idx" type="int" />
 			<description>
 				Sets the size of the array. If the array is grown, reserves elements at the end of the array. If the array is shrunk, truncates the array to the new size.
+				[b]Note:[/b] Added elements are not automatically initialized to 0 and will contain garbage, i.e. indeterminate values.
 			</description>
 		</method>
 		<method name="set">

doc/classes/PoolIntArray.xml

@@ -65,6 +65,7 @@
 			<argument index="0" name="idx" type="int" />
 			<description>
 				Sets the size of the array. If the array is grown, reserves elements at the end of the array. If the array is shrunk, truncates the array to the new size.
+				[b]Note:[/b] Added elements are not automatically initialized to 0 and will contain garbage, i.e. indeterminate values.
 			</description>
 		</method>
 		<method name="set">

doc/classes/PoolRealArray.xml

@@ -65,6 +65,7 @@
 			<argument index="0" name="idx" type="int" />
 			<description>
 				Sets the size of the array. If the array is grown, reserves elements at the end of the array. If the array is shrunk, truncates the array to the new size.
+				[b]Note:[/b] Added elements are not automatically initialized to 0 and will contain garbage, i.e. indeterminate values.
 			</description>
 		</method>
 		<method name="set">