[C++] Remove unused function

Signed-off-by: LiangliangSui <[email protected]>

bazel/arrow/pyarrow_configure.bzl

@@ -2,15 +2,6 @@
 
 # This file is derived from https://github.com/tensorflow/tensorflow/blob/5a244072f2b33d2347e803146c244c179c1ddb75/third_party/py/python_configure.bzl.
 
-def _tpl(repository_ctx, tpl, substitutions = {}, out = None):
-    if not out:
-        out = tpl
-    repository_ctx.template(
-        out,
-        Label("//:%s.tpl" % tpl),
-        substitutions,
-    )
-
 def _fail(msg):
     """Output failure message when auto configuration fails."""
     red = "\033[0;31m"