Remove superfluous "need" from the documentation of buffer module (#1093)

vulkano/src/buffer/mod.rs

@@ -36,7 +36,7 @@
 //! - A [`CpuAccessibleBuffer`](cpu_access/struct.CpuAccessibleBuffer.html) is a simple buffer that
 //!   can be used to prototype. It may be removed from vulkano in the far future.
 //!
-//! Here is a quick way to choose which buffer to use. Do you need to often need to read or write
+//! Here is a quick way to choose which buffer to use. Do you often need to read or write
 //! the content of the buffer? If so, use a `CpuBufferPool`. Otherwise, do you need to be able to
 //! modify the content of the buffer after its initialization? If so, use a `DeviceLocalBuffer`.
 //! If no to both questions, use an `ImmutableBuffer`.