chore: fix a typo

Signed-off-by: hi-rustin <rustin.liu@gmail.com>

src/cargo/core/compiler/custom_build.rs

@@ -10,7 +10,7 @@
 //! that would compile other Cargo targets. It will recursively creates units
 //! of its dependencies. One biggest difference is that the [`Unit`] of
 //! compiling a build script is flagged as [`TargetKind::CustomBuild`].
-//! * Build script executaion --- During the construction of the [`UnitGraph`],
+//! * Build script execution --- During the construction of the [`UnitGraph`],
 //! Cargo inserts a [`Unit`] with [`CompileMode::RunCustomBuild`]. This unit
 //! depends on the unit of compiling the associated build script, to ensure
 //! the executable is available before running. The [`Work`] of running the