rust: exports: improve grammar in commentary

Commit e26fa546 ("rust: kbuild: auto generate helper exports")
added an errant "the" where one was not needed; remove it.

Signed-off-by: Tamir Duberstein <tamird@gmail.com>
Reviewed-by: Dirk Behme <dirk.behme@gmail.com>
Reviewed-by: Alice Ryhl <aliceryhl@google.com>
Reviewed-by: Andreas Hindborg <a.hindborg@kernel.org>
Link: https://lore.kernel.org/r/20241009162358.27735-1-tamird@gmail.com


[ Reworded title. - Miguel ]
Signed-off-by: Miguel Ojeda <ojeda@kernel.org>