Change homebrew/dupes/zlib to zlib

Change `homebrew/dupes/zlib` to `zlib` in the MAC OS installation instruction. using `homebrew/dupes/zlib` shows warning of deprecation.

Logs - 

```

Tapped 0 formulae (30 files, 23.6KB)
Warning: Use zlib instead of deprecated homebrew/dupes/zlib
==> Downloading https://homebrew.bintray.com/bottles/zlib-1.2.11.sierra.bottle.t
######################################################################## 100.0%
==> Pouring zlib-1.2.11.sierra.bottle.tar.gz

```
This commit is contained in:
Girish Ramnani 2017-11-17 17:31:21 +05:30 committed by GitHub
parent 1cd32232a8
commit a24a3702d7
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@ -51,7 +51,7 @@ zlib & libpng (bitmap)
Xcode Command Line Tools
```
brew install libpng
brew install homebrew/dupes/zlib
brew install zlib
```
#### For Windows:
```