Update docs/content/instrumenting/gauge.md

Co-authored-by: Chris Marchbanks <csmarchbanks@gmail.com>
Signed-off-by: Lukáš Vokráčko <lukas@vokracko.cz>

Author: vokracko

docs/content/instrumenting/gauge.md

@@ -111,7 +111,7 @@ with g.time():
 
 with g.time() as t:
     pass
-# t.duration holds the observed seconds
+print(t.duration) # observed time in seconds.
 ```
 
 ### `set_function(f)`