Add documentation around pallet coupling (paritytech#3542)

substrate.io deprecation companion:
polkadot-developers/substrate-docs#2139
pba-content companion:
Polkadot-Blockchain-Academy/pba-content#978

partially inspired by:
paritytech#3535

---------

Co-authored-by: Ankan <10196091+Ank4n@users.noreply.github.com>

substrate/frame/support/src/lib.rs

@@ -1531,9 +1531,8 @@ pub mod pallet_macros {
 	/// The attribute currently only supports enum definitions, and identifiers that are named
 	/// `FreezeReason`, `HoldReason`, `LockId` or `SlashReason`. Arbitrary identifiers for the
 	/// enum are not supported. The aggregate enum generated by
-	/// [`frame_support::construct_runtime`](frame_support::construct_runtime) will have the
-	/// name of `RuntimeFreezeReason`, `RuntimeHoldReason`, `RuntimeLockId` and
-	/// `RuntimeSlashReason` respectively.
+	/// [`frame_support::construct_runtime`] will have the name of `RuntimeFreezeReason`,
+	/// `RuntimeHoldReason`, `RuntimeLockId` and `RuntimeSlashReason` respectively.
 	///
 	/// NOTE: The aggregate enum generated by `construct_runtime` generates a conversion
 	/// function from the pallet enum to the aggregate enum, and automatically derives the