docs: Fix grammar in templates/partials.md

Noticed this sentence seemingly missing a word or two.

content/templates/partials.md

@@ -122,6 +122,6 @@ As you might have noticed, `partial` calls receive two paramters.
 location to be read.
 2. The second is the variables to be passed down to the partial.
 
-This means the partial _only_ be able to access those variables. It is
+This means that the partial will _only_ be able to access those variables. It is
 isolated and has no access to the outer scope. From within the
 partial, `$.Var` is equivalent to `.Var`