bot docs: Migrate script name from zulip-terminal to zulip-bot-shell.
bot docs: Migrate script name from zulip-terminal to zulip-bot-shell.

This change is intended to reduce confusion between zulip-bot-shell
(test bots interactively without a server) and the zulip/zulip-terminal
project and its associated command (zulip-term).

andersk/zulip,zulip/zulip,zulip/zulip,rht/zulip,rht/zulip,eeshangarg/zulip,eeshangarg/zulip,zulip/zulip,andersk/zulip,andersk/zulip,kou/zulip,rht/zulip,eeshangarg/zulip,zulip/zulip,zulip/zulip,eeshangarg/zulip,andersk/zulip,rht/zulip,zulip/zulip,zulip/zulip,rht/zulip,rht/zulip,kou/zulip,kou/zulip,kou/zulip,eeshangarg/zulip,andersk/zulip,andersk/zulip,kou/zulip,eeshangarg/zulip,andersk/zulip,rht/zulip,kou/zulip,kou/zulip,eeshangarg/zulip