GH Actions: Remove codecov token #100

Job	Run time
Check (libp2p)	2m 46s
Check (waku)	5m 8s
Rust lints (libp2p)	2m 30s
Rust lints (waku)	6m 11s
Test Suite (libp2p, ubuntu-latest)	10m 30s
Test Suite (libp2p, windows-latest)	16m 53s
Test Suite (libp2p, macos-latest)	15m 38s
Test Suite (waku, ubuntu-latest)	13m 40s
Test Suite (waku, windows-latest)	14m 44s
Test Suite (waku, macos-latest)	17m 29s
	1h 45m 29s

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