Minor update to Readme - Statemint section (#2078)

* Minor update to Readme - Statemint section

Common good -> System

* update parchains readme

* Update parachains/README.md

Co-authored-by: Bastian Köcher <git@kchr.de>

Co-authored-by: joe petrowski <25483142+joepetrowski@users.noreply.github.com>
Co-authored-by: Bastian Köcher <git@kchr.de>

README.md

@@ -120,7 +120,7 @@ cargo build --release --bin polkadot-parachain
 
 This repository also contains the Statemint runtime (as well as the canary runtime Statemine and the
 test runtime Westmint).
-Statemint is a common good parachain providing an asset store for the Polkadot ecosystem.
+Statemint is a system parachain providing an asset store for the Polkadot ecosystem.
 
 ### Build & Launch a Node
 

parachains/README.md

@@ -11,11 +11,11 @@ The general internal structure is:
 - `pallets`: FRAME pallets that are specific to parachains.
 - `runtimes`: The entry point for parachain runtimes.
 
-## Common Good Parachains
+## System Parachains
 
 The `runtimes` directory includes many, but is not limited to,
-[common good parachains](https://wiki.polkadot.network/docs/learn-common-goods). Likewise, not all
-common good parachains are in this repo.
+[system parachains](https://wiki.polkadot.network/docs/learn-system-chains). Likewise, not all
+system parachains are in this repo.
 
 ## Releases