Fix typo in Contributing.md & Cluster+Membership.swift (#1204)

### Motivation: Fix typo in Contributing.md & Cluster+Membership.swift ### Modifications: Change byt to but. Add a space after (Unique). ### Result: Removed typos.

Author: zaneenders

Sources/DistributedCluster/Cluster/Cluster+Membership.swift

@@ -23,7 +23,7 @@ extension Cluster {
  /// Membership changes are driven by nodes joining and leaving the cluster.
  /// Leaving the cluster may be graceful or triggered by a failure detector.
  ///
- /// ### Replacement (Unique)Nodes
+ /// ### Replacement (Unique) Nodes
  /// A node (or member) is referred to as a "replacement" if it shares _the same_ protocol+host+address (i.e. ``Cluster/Endpoint``),
  /// with another member; It MAY join "over" an existing node and will immediately cause the previous node to be marked ``Cluster/MemberStatus/down``
  /// upon such transition. Such situations can take place when an actor system node is terminated and started on the same host+port immediately,

Sources/DistributedCluster/Docs.docc/Contributing.md

@@ -16,7 +16,7 @@ Multi node test infrastructure is still in development and may be lacking some f
 
 ### Testing logging (LogCapture)
 
-As the cluster performs operations "in the background", such as keeping the membership and health information of the cluster up to date, it is very important that log statements it emits in such mode are useful and actionable, byt not overwhelming.
+As the cluster performs operations "in the background", such as keeping the membership and health information of the cluster up to date, it is very important that log statements it emits in such mode are useful and actionable, but not overwhelming.
 
 > Note: Almost all tests spanning multiple actor systems use a form of log capture, in order to keep the test output clean. Only some tests actually assert on logged information.