Fix a missing space in a recently merged PR #520 (#527)

Author: JuliaMongo

source/reference/production-notes.txt

@@ -287,7 +287,7 @@ for the MongoDB Pod as follows:
 
 If you don't include the unit of measurement for CPUs, |k8s| interprets
 it as the number of cores. If you specify ``m``, such as 500m, |k8s|
-interprets it as``millis``. To learn more, see
+interprets it as ``millis``. To learn more, see
 :k8sdocs:`Meaning of CPU </concepts/configuration/manage-resources-containers/#meaning-of-cpu>`.
 
 The following abbreviated example shows the configuration with