Fix README formatting

nav2_system_tests/src/updown/README.md

@@ -13,8 +13,10 @@ If the test passes, you should see this comment in the output:
 ```
 
 To run the test in a loop 1000x, run the `test_updown_reliablity` script and log the output:
-` > ./test_updown_reliablity |& tee /tmp/updown.log`
-
+```
+./test_updown_reliablity |& tee /tmp/updown.log
+```
 When the test is completed, pipe the log to the `updownresults.py` script to get a summary of the results:
-` > ./updownresults.py < /tmp/updown.log`
-
+```
+./updownresults.py < /tmp/updown.log`
+```