Remove variables which are never read (#657)

changelog.d/657.misc

package.json

src/bot.ts

src/db/roomstore.ts

src/db/schema/v8.ts

src/matrixcommandhandler.ts

src/matrixeventprocessor.ts

src/matrixmessageprocessor.ts

src/matrixroomhandler.ts

test/db/test_roomstore.ts

test/mocks/channel.ts

test/mocks/discordclient.ts

test/test_discordmessageprocessor.ts

test/test_presencehandler.ts

yarn.lock