(DOCSP-15050) Update mongocli to golang 1.16 (#492)

Author: zach-carr

source/install.txt

@@ -69,7 +69,7 @@ To install the {+mcli+}, choose one of the following methods:
 
       1. `Git <https://git-scm.com/book/en/v2/Getting-Started-Installing-Git>`_.
 
-      #. `Go v1.15 or newer <https://golang.org/doc/install#install>`_.
+      #. `Go v1.16 or newer <https://golang.org/doc/install#install>`_.
 
 Procedure
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