Correct spelling: boudary => boundary

Change-Id: If8f9d5221f7ee82dcc88286f86cbcc3b42a72f83
diff --git a/av1/encoder/var_based_part.c b/av1/encoder/var_based_part.c
index 16e53fd..94ddfa9 100644
--- a/av1/encoder/var_based_part.c
+++ b/av1/encoder/var_based_part.c
@@ -596,7 +596,7 @@
         thresholds[2] <<= 3;
       }
       // Allow for split to 8x8 for superblocks where part of it has
-      // moving boudary. So allow for sb with source_sad above threshold,
+      // moving boundary. So allow for sb with source_sad above threshold,
       // and avoid very large source_sad or high source content, to avoid
       // too many 8x8 within superblock.
       if (segment_id == 0 && cpi->rc.avg_source_sad < 25000 &&