CLEANUP: Fix typos in the shctx subsystem

Fixes typos in the code comments of the shctx subsystem.
diff --git a/src/shctx.c b/src/shctx.c
index 9fe12e8..fe1b74a 100644
--- a/src/shctx.c
+++ b/src/shctx.c
@@ -243,7 +243,7 @@
 
 /*
  * Copy <len> data from a row of blocks, return the remaining data to copy
- * If 0 is returned, the full data has successfuly be copied
+ * If 0 is returned, the full data has successfully been copied
  *
  * The row should be in the hot list
  */