fbcode_builder: getdeps: fboss remove OpenNSL manifest

Summary:
Broadcom has formally replaced OpenNSL with newer OpenNSA:
https://github.com/Broadcom-Network-Switching-Software/OpenNSA/blob/master/README.md

With D16401189, FBOSS no longer depends on OpenNSL, but uses the new OpenNSA
instead. Remove this manifest.

Reviewed By: wez

Differential Revision: D19413708

fbshipit-source-id: f3662f1101d59a5e0e59cb7238797d652564ff90

build/fbcode_builder/manifests/OpenNSL

-[manifest]
-name = OpenNSL
-
-[download]
-url = https://github.com/Broadcom-Switch/OpenNSL/archive/v3.5.0.1.tar.gz
-sha256 = 00e5367a479c160aa273e4da4b978d5e38132324c8ea960cc1b142d048dad5f8
-
-[build]
-builder = nop
-subdir = OpenNSL-3.5.0.1
-
-[install.files]
-bin/wedge = lib
-include = include