Update project-variables.md (#5387)

Hi.
This modification proposal is to change "four" by "five" since that's
the number of options at:
https://docs.getdbt.com/docs/build/project-variables#variable-precedence.
It seems as if having left this part of old code:
<VersionBlock lastVersion="1.5">
, might have confused the developer.
At present, the text inside this code:
<VersionBlock firstVersion="1.6">
, is the one displayed in the docs.
Regards.
IL.

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---------

Co-authored-by: Mirna Wong <[email protected]>
Co-authored-by: Leona B. Campbell <[email protected]>

website/docs/docs/build/project-variables.md

@@ -110,7 +110,7 @@ The order of precedence for variable declaration is as follows (highest priority
 
 </VersionBlock>
 
-If dbt is unable to find a definition for a variable after checking these four places, then a compilation error will be raised.
+If dbt is unable to find a definition for a variable after checking all possible variable declaration places, then a compilation error will be raised.
 
 **Note:** Variable scope is based on the node ultimately using that variable. Imagine the case where a model defined in the root project is calling a macro defined in an installed package. That macro, in turn, uses the value of a variable. The variable will be resolved based on the _root project's_ scope, rather than the package's scope.