Remove outdated mention of hg.exe from Tools/msi/README.txt (GH-17792)

diff --git a/Tools/msi/README.txt b/Tools/msi/README.txt
index f5656b9..82635f3 100644
--- a/Tools/msi/README.txt
+++ b/Tools/msi/README.txt
@@ -11,7 +11,7 @@
 
     set PYTHON=<path to Python 2.7 or 3.4>
     set SPHINXBUILD=<path to sphinx-build.exe>
-    set PATH=<path to Mercurial (hg.exe)>;
+    set PATH=<path to Git (git.exe)>;
              <path to HTML Help Compiler (hhc.exe)>;%PATH%
 
     buildrelease.bat [-x86] [-x64] [-D] [-B]
@@ -106,7 +106,7 @@
 
     set PYTHON=<path to Python 2.7 or 3.4>
     set SPHINXBUILD=<path to sphinx-build.exe>
-    set PATH=<path to Mercurial (hg.exe)>;
+    set PATH=<path to Git (git.exe)>;
              <path to HTML Help Compiler (hhc.exe)>;%PATH%
 
     buildrelease.bat [-x86] [-x64] [-D] [-B]
@@ -131,7 +131,7 @@
 
 Ensure %PYTHON% and %SPHINXBUILD% are set when passing this option. You
 may also set %HTMLHELP% to the Html Help Compiler (hhc.exe), or put HHC
-on your PATH or in externals/. You will also need Mercurial (hg.exe) on
+on your PATH or in externals/. You will also need Git (git.exe) on
 your PATH.
 
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