"OS X" -> macOS in install instructions

Author: ajdavis

docs/content/mongocxx-v3/index.md

@@ -12,7 +12,7 @@ slug = "index"
 
 The mongocxx is a ground-up rewrite of a C++ driver for MongoDB based on
 [libmongoc](http://mongoc.org/).  It requires a C++11 compiler.  It it
-known to build on x86 and x86-64 architectures for Linux, Mac OS X,
+known to build on x86 and x86-64 architectures for Linux, macOS,
 Windows, FreeBSD and Solaris.
 
 The mongocxx driver library includes a matching bson package, bsoncxx, that

docs/content/mongocxx-v3/installation.md

@@ -17,7 +17,7 @@ title = "Installing the mongocxx driver"
 
 We currently test the driver with the following configurations:
 
-  |   Linux  |    OS X     |      Windows
+  |   Linux  |    macOS    |      Windows
 -------|----------|-------------|-------------------
  clang |   3.8    | 7.0 (Apple) |        -
  gcc   | 4.8, 5.4 |     -       |        -
@@ -53,7 +53,7 @@ Follow the instructions for building from a tarball at
 
 Industry best practices and some regulations require the use of TLS 1.1
 or newer. The MongoDB C Driver supports TLS 1.1 on Linux if OpenSSL is
-at least version 1.0.1. On OS X and Windows, the C Driver uses native
+at least version 1.0.1. On macOS and Windows, the C Driver uses native
 TLS implementations that support TLS 1.1.
 
 ### Step 2: Choose a C++17 polyfill