Minor Grammatical correction (#27742)

* Minor Grammatical correction

* Correcting, as per PR suggestion

docs/sources/tutorials/stack_guide_graphite.md

@@ -17,7 +17,7 @@ database has yet to match Graphite's query flexibility and analytics potential.
 Graphite has a reputation for being tricky to install and scale. This guide aims to show
 that is not really the case, or, at least, that it is a lot better than you expect.
 
-> This guide does not only aim to be only be an install guide but to also teach you
+> This is an install guide that also teaches you
 > of the mechanics of metric collection, aggregation and querying. How Graphite
 > stores and aggregates data is very important to understand in order to not
 > get mislead by graphs.