Fix jira key in PR template

Author: slawekjaranowski

.github/pull_request_template.md

@@ -1,13 +1,13 @@
 Following this checklist to help us incorporate your 
 contribution quickly and easily:
 
- - [ ] Make sure there is a [JIRA issue](https://issues.apache.org/jira/browse/MPH) filed 
+ - [ ] Make sure there is a [JIRA issue](https://issues.apache.org/jira/browse/MDEPLOY) filed 
        for the change (usually before you start working on it).  Trivial changes like typos do not 
        require a JIRA issue.  Your pull request should address just this issue, without 
        pulling in other changes.
  - [ ] Each commit in the pull request should have a meaningful subject line and body.
- - [ ] Format the pull request title like `[MPH-XXX] - Fixes bug in ApproximateQuantiles`,
-       where you replace `MPH-XXX` with the appropriate JIRA issue. Best practice
+ - [ ] Format the pull request title like `[MDEPLOY-XXX] - Fixes bug in ApproximateQuantiles`,
+       where you replace `MDEPLOY-XXX` with the appropriate JIRA issue. Best practice
        is to use the JIRA issue title in the pull request title and in the first line of the 
        commit message.
  - [ ] Write a pull request description that is detailed enough to understand what the pull request does, how, and why.