Update Infinity API doc to reflect optional `accessTime`
Update Infinity API doc to reflect optional `accessTime`

We changed the code to make `accessTime` field of `AbstractMetadata`
optional. This change also modifies the documentation to reflect that
change.

telefonicaid/fiware-cosmos-platform,telefonicaid/fiware-cosmos-platform,telefonicaid/fiware-cosmos-platform,telefonicaid/fiware-cosmos-platform,telefonicaid/fiware-cosmos-platform