Fix compile warning in telemetry_test.exs
Fixes the following warnings:
warning: variable "path" is unused (if the variable is not meant to be used, prefix it with an underscore)
test/tesla/middleware/telemetry_test.exs:46: Tesla.Middleware.TelemetryTest."test events are all emitted properly"/1
warning: variable "path" is unused (if the variable is not meant to be used, prefix it with an underscore)
test/tesla/middleware/telemetry_test.exs:49: Tesla.Middleware.TelemetryTest."test events are all emitted properly"/1
warning: variable "result" is unused (if the variable is not meant to be used, prefix it with an underscore)
test/tesla/middleware/telemetry_test.exs:51: Tesla.Middleware.TelemetryTest."test events are all emitted properly"/1
warning: variable "time" is unused (if the variable is not meant to be used, prefix it with an underscore)
test/tesla/middleware/telemetry_test.exs:45: Tesla.Middleware.TelemetryTest."test events are all emitted properly"/1
warning: variable "time" is unused (if the variable is not meant to be used, prefix it with an underscore)
test/tesla/middleware/telemetry_test.exs:48: Tesla.Middleware.TelemetryTest."test events are all emitted properly"/1
warning: variable "time" is unused (if the variable is not meant to be used, prefix it with an underscore)
test/tesla/middleware/telemetry_test.exs:51: Tesla.Middleware.TelemetryTest."test events are all emitted properly"/1
warning: variable "kind" is unused (if the variable is not meant to be used, prefix it with an underscore)
test/tesla/middleware/telemetry_test.exs:66: Tesla.Middleware.TelemetryTest."test with an exception raised"/1
warning: variable "reason" is unused (if the variable is not meant to be used, prefix it with an underscore)
test/tesla/middleware/telemetry_test.exs:67: Tesla.Middleware.TelemetryTest."test with an exception raised"/1
warning: variable "stacktrace" is unused (if the variable is not meant to be used, prefix it with an underscore)
test/tesla/middleware/telemetry_test.exs:68: Tesla.Middleware.TelemetryTest."test with an exception raised"/1
warning: variable "time" is unused (if the variable is not meant to be used, prefix it with an underscore)
test/tesla/middleware/telemetry_test.exs:64: Tesla.Middleware.TelemetryTest."test with an exception raised"/1