Revert "Make mojo_shell depend on NSS on Linux."
Revert "Make mojo_shell depend on NSS on Linux."

We changed the approach and fixed the NSS issue in the network service
in https://codereview.chromium.org/962593002/ .

We don't need this hack anymore.

BUG=456130

This reverts commit d10ab90c3c74c6e85cbe8817fc1b8b178ab7ad73.

R=qsr@chromium.org

Review URL: https://codereview.chromium.org/979773002

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