Title Case the heading in the brew(1) man page template

- Without this, `brew man` produces a lowercasing diff that violates
  Vale's rules.
- Also run `brew man` to test this out, and that updated some dates to
  December.

Library/Homebrew/manpages/brew.1.md.erb

@@ -9,7 +9,7 @@
 #
 # When done, regenerate the man page and its HTML version by running `brew man`.
 %>
-brew(1) -- The missing package manager for macOS
+brew(1) -- The Missing Package Manager for macOS
 ================================================
 
 ## SYNOPSIS

manpages/brew.1

@@ -4,7 +4,7 @@
 .TH "BREW" "1" "December 2019" "Homebrew" "brew"
 .
 .SH "NAME"
-\fBbrew\fR \- The missing package manager for macOS
+\fBbrew\fR \- The Missing Package Manager for macOS
 .
 .SH "SYNOPSIS"
 \fBbrew\fR \fB\-\-version\fR