Doc - fix issue #4778 (#5081)

Documentation/Books/AQL/Operations/Collect.md

@@ -164,13 +164,10 @@ FOR u IN users
   RETURN length
 ```
 
-The above is equivalent to, but more efficient than:
+The above is equivalent to, but less efficient than:
 
 ```
-RETURN LENGTH(
-  FOR u IN users
-    RETURN length
-)
+RETURN LENGTH(users)
 ```
 
 The *WITH COUNT* clause can also be used to efficiently count the number

Documentation/Books/AQL/Operations/Insert.md

@@ -98,7 +98,8 @@ documents. For each inserted document, the document key is returned:
 
 ```js
 FOR i IN 1..100
-  INSERT { value: i } 
+  INSERT { value: i }
+  IN users 
   LET inserted = NEW 
   RETURN inserted._key
 ```

Documentation/Books/AQL/Operations/Update.md

@@ -233,7 +233,8 @@ documents before modification. For each modified document, the document key is r
 
 ```js
 FOR u IN users
-  UPDATE u WITH { value: "test" } 
+  UPDATE u WITH { value: "test" }
+  IN users 
   LET previous = OLD 
   RETURN previous._key
 ```
@@ -244,6 +245,7 @@ without some of the system attributes:
 ```js
 FOR u IN users
   UPDATE u WITH { value: "test" } 
+  IN users
   LET updated = NEW 
   RETURN UNSET(updated, "_key", "_id", "_rev")
 ```
@@ -253,5 +255,6 @@ It is also possible to return both `OLD` and `NEW`:
 ```js
 FOR u IN users
   UPDATE u WITH { value: "test" } 
+  IN users
   RETURN { before: OLD, after: NEW }
 ```