Nexus sample README edits (#729)

Author: dandavison

core/src/main/java/io/temporal/samples/nexuscancellation/README.MD

@@ -2,9 +2,9 @@
 
 This sample shows how to cancel a Nexus operation from a caller workflow.
 
-From more details on Nexus and how to setup to run this samples please see the [Nexus Sample](../nexus/README.MD).
+To run this sample, set up your environment following the instructions in the main [Nexus Sample](../nexus/README.md).
 
-In separate terminal windows:
+Next, in separate terminal windows:
 
 ### Nexus handler worker
 

core/src/main/java/io/temporal/samples/nexuscontextpropagation/README.MD

@@ -1,11 +1,11 @@
 # Nexus Context Propagation
 
-This sample shows how to propagate MDC context values from Workflows to Nexus operations. 
+This sample shows how to propagate MDC (Mapped Diagnostic Context) context values from Workflows to Nexus operations.
 Nexus does not support `ContextPropagator` since the header format is not compatible. Users should look at `NexusMDCContextInterceptor` for propagating MDC context values.
 
-From more details on Nexus and how to setup to run this samples please see the [Nexus Sample](../nexus/README.MD).
+To run this sample, set up your environment following the instructions in the main [Nexus Sample](../nexus/README.md).
 
-In separate terminal windows:
+Next, in separate terminal windows:
 
 ### Nexus handler worker