Remove @brief annotations from Rust API docs (#20769)

programs/bpf/rust/mem/src/entrypoint.rs

@@ -1,4 +1,4 @@
-//! @brief Test mem functions
+//! Test mem functions
 
 use crate::{run_mem_tests, MemOps};
 use solana_program::{

programs/bpf/rust/mem/src/lib.rs

@@ -1,4 +1,4 @@
-//! @brief Test mem functions
+//! Test mem functions
 
 #[cfg(not(feature = "no-entrypoint"))]
 pub mod entrypoint;