Fix trimmed network string

[DaniPopes]

Current output lists networks with the last character chopped off which looks very funny:

usage: slither target [flag]

target can be:
	- file.sol // a Solidity file
	- project_directory // a project directory. See https://github.com/crytic/crytic-compile/#crytic-compile for the supported platforms
	- 0x.. // a contract on mainnet
	- NETWORK:0x.. // a contract on a different network. Supported networks: mainne,sepoli,holesk,bs,testnet.bs,pol,amoy.pol,polyz,cardona.polyz,bas,sepolia.bas,arb,nova.arb,sepolia.arb,line,sepolia.line,ft,testnet.ft,blas,sepolia.blas,opti,sepolia.opti,ava,testnet.ava,btt,testnet.btt,cel,alfajores.cel,crono,fra,holesky.fra,gn,krom,sepolia.krom,mantl,sepolia.mantl,moonbea,moonrive,moonbas,opbn,testnet.opbn,scrol,sepolia.scrol,taik,hekla.taik,wemi,testnet.wemi,era.zksyn,sepoliaera.zksyn,xa,sepolia.xa,xd,testnet.xd,apechai,curtis.apechai,worl,sepolia.worl,sopho,testnet.sopho,soni,testnet.soni,unichai,sepolia.unichai,abstrac,sepolia.abstrac,berachai

[CLAassistant]

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