Remove calling other contracts (#22)

Author: calummoore

collections.mdx

@@ -175,37 +175,6 @@ const col = db.collection("account");
 await col.record("id1").call("transfer", [c.record("id2"), 10]);
 ```
 
-### Calling other collections
-
-You can define a parameter of a function to accept a record from another collection, allowing you 
-to perform atomic updates to multiple records from different collections.
-
-```js 
-collection Account {
-  id: string;
-  name?: string;
-
-  constructor (id: string, counter: Counter) {
-    this.id = ctx.publicKey;
-    counter.incr()
-  }
-}
-
-collection Counter {
-  id: string;
-  count: number;
-
-  constructor (id: string) {
-    this.id = id;
-    this.count = 0;
-  }
-
-  incr () {
-    this.count += 1;
-  }
-}
-```
-
 
 ### Indexes