Fix grammar issue (couchbase/docs-server#2785)

* Typo `can trigger` repeating twice in the `Eventing Keyspaces` section
* As we only have Data Service, let us be consistent across as Data Service provider seems like another term for Data Service
* Added language feature incorrectly positioned in the removed language features list
* Add item under language restriction; importing libraries is not allowed
* Import libs is restricted
* Fix grammar issue in eventing-language-constructs
* CAS is allowed to be set, albeit, it is a no-op in the upsert operation. Hence it is incorrect to document that upsert does not allow setting CAS for the document.
* Fix grammar issue in eventing-timers.adoc
* Updates after review

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Co-authored-by: Simon Dew <[email protected]>

Author: simon-dew

modules/eventing/pages/eventing-timers.adoc

@@ -3,7 +3,7 @@
 :page-edition: Enterprise Edition
 
 {description}
-Timers also measure and track the amount of elapsed time and can be used while archiving of expired documents at a preconfigured time.
+Timers also measure and track the amount of elapsed time and can be used while archiving expired documents at a preconfigured time.
 
 NOTE: When using timers, it is required that all nodes of the cluster are synchronized at computer startup, and periodically afterwards using a clock synchronization tool like NTP.