[DOCS] made it clearer that the _version is incremented by all write operations (deletes included)

docs/reference/docs/delete.asciidoc

@@ -31,7 +31,8 @@ The result of the above delete operation is:
 Each document indexed is versioned. When deleting a document, the
 `version` can be specified to make sure the relevant document we are
 trying to delete is actually being deleted and it has not changed in the
-meantime.
+meantime. Every write operation executed on a document, deletes included,
+causes its version to be incremented.
 
 [float]
 [[delete-routing]]

docs/reference/docs/index_.asciidoc

@@ -106,11 +106,11 @@ near real time aspects of search operations. If no version is provided,
 then the operation is executed without any version checks.
 
 By default, internal versioning is used that starts at 1 and increments
-with each update. Optionally, the version number can be supplemented
-with an external value (for example, if maintained in a database). To
-enable this functionality, `version_type` should be set to `external`.
-The value provided must be a numeric, long value greater than 0, and
-less than around 9.2e+18. When using the external version type, instead
+with each update, deletes included. Optionally, the version number can be
+supplemented with an external value (for example, if maintained in a
+database). To enable this functionality, `version_type` should be set to
+`external`. The value provided must be a numeric, long value greater than 0,
+and less than around 9.2e+18. When using the external version type, instead
 of checking for a matching version number, the system checks to see if
 the version number passed to the index request is greater than the
 version of the currently stored document. If true, the document will be