Revert "Update the instructions for TF C API package"
Revert "Update the instructions for TF C API package"

This reverts commit 7471653207f50f36a2b52081f3cdcfc2316ecf68.

We need TF C API v1.15 because 2.6 is linked incorrectly.

google/ml-compiler-opt,google/ml-compiler-opt