Remove "browser" from package.json to fix Browserify

[nolanlawson]

I tried to follow the discussion from less#2525, but wasn't really understanding why this was added in the first place.

Using Browserify 11.1.0, it's impossible to use less @2.5.1 as part of your build. I can reproduce it as easily as:

npm install less
echo "require('less')" > index.js
browserify index.js

You'll see the error:

Error: Cannot find module './utils' from '/private/tmp/fdlsjlkfsd/node_modules/less/dist'
    at /Users/nolan/.npm-packages/lib/node_modules/browserify/node_modules/resolve/lib/async.js:55:21
    at load (/Users/nolan/.npm-packages/lib/node_modules/browserify/node_modules/resolve/lib/async.js:69:43)
    at onex (/Users/nolan/.npm-packages/lib/node_modules/browserify/node_modules/resolve/lib/async.js:92:31)
    at /Users/nolan/.npm-packages/lib/node_modules/browserify/node_modules/resolve/lib/async.js:22:47
    at FSReqWrap.oncomplete (fs.js:82:15)

This commit fixes that.