Remove vestigial lines.

- The preamble comments didn't follow the preamble/end convention, and
  it isn't worth shuffling lines to find a place to add an end marker.
- The `-*- coding` text seems unnecessary, and is confusing an editor
  into thinking the .lua files are written in C.

git.lua

@@ -1,5 +1,3 @@
--- preamble: common routines
-
 local path_module = require('path')
 local git = require('gitutil')
 local matchers = require('matchers')

pip.lua

@@ -1,6 +1,3 @@
--- -*- coding: utf-8 -*-
--- preamble: common routines
-
 local matchers = require("matchers")
 local w = require("tables").wrap
 

pipenv.lua

@@ -1,6 +1,3 @@
--- -*- coding: utf-8 -*-
--- preamble: common routines
-
 local matchers = require("matchers")
 local w = require("tables").wrap
 local concat = require("funclib").concat

scoop.lua

@@ -1,6 +1,3 @@
--- -*- coding: utf-8 -*-
--- preamble: common routines
-
 local JSON = require("JSON")
 
 local matchers = require("matchers")