[mlir][Linalg] Delete unused LinalgLibraryOps.td

Summary: This has been previously renamed to LinalgStructuredOps.td

Reviewers: ftynse

Subscribers: mehdi_amini, rriddle, jpienaar, burmako, shauheen, antiagainst, llvm-commits, ftynse

Tags: #llvm

Differential Revision: https://reviews.llvm.org/D72013