Correct the description of compilation time

Author: joshtriplett

content/inside-rust/call-for-testing-hint-mostly-unused.md

@@ -25,7 +25,7 @@ linker then ends up throwing most of that code away as unused.
 This can waste a substantial amount of compile time. Some large crates can take
 minutes to compile, and when you use these large crates as dependencies, they
 can take a disproportionate amount of the entire compilation time of your
-top-level crate.
+overall build.
 
 In some cases, crates add feature flags to control compilation of their API
 surface. This can improve compile time, but adds complexity for users, who now