fix(docs): minimum rust version mismatch in lib.rs

Author: HoKim98

src/lib.rs

@@ -71,7 +71,7 @@
 //!     needs matching memory layout to be efficient (with some exceptions).
 //!   + Efficient floating point matrix multiplication even for very large
 //!     matrices; can optionally use BLAS to improve it further.
-//! - **Requires Rust 1.49 or later**
+//! - **Requires Rust 1.51 or later**
 //!
 //! ## Crate Feature Flags
 //!