Scripts and tools: Drop no-longer-relevant copyright holder names

Summary:
Now that leveldb, secp256k1, etc. are reliably excluded, these
names will not show up in the searched files.

This is a backport of core#15258 [2/2]
https://github.com/bitcoin/bitcoin/pull/15258/commits/ad5e5a105e873b6cca277370312d3d31a3427d38

Depends on D9810

Test Plan: ./contrib/devtools/copyright_header.py report .

Reviewers: #bitcoin_abc, Fabien

Reviewed By: #bitcoin_abc, Fabien

Differential Revision: https://reviews.bitcoinabc.org/D9811