[Bazel] Delete deprecated gentbl rule

This has been deprecated for a while. There are no users in tree and I'm
not aware of any out of tree users either.

Reviewed By: ftynse

Differential Revision: https://reviews.llvm.org/D106114

utils/bazel/llvm-project-overlay/mlir/tblgen.bzl

@@ -436,45 +436,3 @@ def gentbl_cc_library(
         textual_hdrs = [":" + filegroup_name],
         **kwargs
     )
-
-def gentbl(
-        name,
-        tblgen,
-        td_file,
-        tbl_outs,
-        td_srcs = [],
-        td_includes = [],
-        includes = [],
-        td_relative_includes = [],
-        deps = [],
-        test = False,
-        **kwargs):
-    """Deprecated version of gentbl_cc_library.
-
-    Accepts tbl_outs as list of pairs with the first element of the pair being
-    a whitespace-separated string of options rather than a list of options.
-    """
-
-    split_opts = []
-    for (opts_string, out) in tbl_outs:
-        opts = opts_string.split(" ") if opts_string else []
-
-        # Filter out empty options
-        opts = [opt for opt in opts if opt]
-
-        split_opts.append((opts, out))
-
-    gentbl_cc_library(
-        name = name,
-        tblgen = tblgen,
-        td_file = td_file,
-        tbl_outs = split_opts,
-        td_srcs = td_srcs,
-        td_includes = td_includes,
-        includes = includes,
-        td_relative_includes = td_relative_includes,
-        deps = deps,
-        test = test,
-        deprecation = "generated by gentbl; use gentbl_cc_library or gentbl_filegroup instead",
-        **kwargs
-    )