let's be truer.

Signed-off-by: Gabi Davar <grizzly.nyo@gmail.com>

Author: mindw

README.md

@@ -79,7 +79,7 @@ Github Project Page](http://prometheus.github.io/client_java).
 By default, counters, histograms, and summaries export an additional series
 suffixed with `_created` and a value of the unix timestamp for when the metric
 was created. If this information is not helpful, it can be disabled by setting
-the environment variable `PROMETHEUS_DISABLE_CREATED_SERIES=True`.
+the environment variable `PROMETHEUS_DISABLE_CREATED_SERIES=true`.
 
 ## Instrumenting