update docs about --oom-score-adj

Signed-off-by: allencloud <allen.sun@daocloud.io>

docs/reference/run.md

@@ -836,7 +836,7 @@ The container has unlimited memory which can cause the host to run out memory
 and require killing system processes to free memory. The `--oom-score-adj`
 parameter can be changed to select the priority of which containers will
 be killed when the system is out of memory, with negative scores making them
-less likely to be killed an positive more likely.
+less likely to be killed, and positive scores more likely.
 
 ### Kernel memory constraints