Remove invalid assertion from mcomp.c

The frame width is not necessarily the same between the reference
frame and the source frame. The stride is though.

BUG=aomedia:3527

Change-Id: I44d760e86ee6aa5918b7640498375e4cf0633736
(cherry picked from commit c7986e6b2271d5bd2e286b6c056653e4f761c144)

av1/encoder/mcomp.c

diff --git a/av1/encoder/mcomp.c b/av1/encoder/mcomp.c
index a8b0d10..2462f1b 100644
--- a/av1/encoder/mcomp.c
+++ b/av1/encoder/mcomp.c
@@ -1807,7 +1807,6 @@
   }
 
   assert(ms_params->ms_buffers.ref->stride == ms_params->search_sites->stride);
-  assert(ms_params->ms_buffers.ref->width == ms_params->ms_buffers.src->width);
 
   switch (search_method) {
     case FAST_BIGDIA: