[bazel] Fix bazel test by specifying unroll-elements.mlir as data (#158158)
`mlir/test/Dialect/Vector/td/unroll-elements.mlir` is fed as a data
dependency
into`mlir/test/Dialect/Vector/vector-to-elements-lowering.mlir` added in
[#157142](https://github.com/llvm/llvm-project/pull/157142). The Bazel
rule here automatically picks up all mlir files as tests, which leads to
`vector-to-elements-lowering` failing.