Merge #10036: Fix init README format to render correctly on github

Summary:
b99fbad Fix init README format to render correctly on github (Jameson Lopp)

Tree-SHA512: 52b8ed9661e48e830c9e0c0e9aa670fe8d1a3848426d2d854494b477a9926f286d87e0586c2bc63f433136f8e5acd2cab3ab1f616380fb517c5a8f9d34ed52da

Backport of Core PR10036
https://github.com/bitcoin/bitcoin/pull/10036/files

Test Plan: Read it.

Reviewers: #bitcoin_abc, deadalnix, Fabien

Reviewed By: #bitcoin_abc, Fabien

Differential Revision: https://reviews.bitcoinabc.org/D3843

contrib/init/README.md

@@ -1,12 +1,12 @@
 Sample configuration files for:
-
+```
 SystemD: bitcoind.service
 Upstart: bitcoind.conf
 OpenRC:  bitcoind.openrc
          bitcoind.openrcconf
 CentOS:  bitcoind.init
 OS X:    org.bitcoin.bitcoind.plist
-
+```
 have been made available to assist packagers in creating node packages here.
 
 See doc/init.md for more information.