minor #144 [Maintenance] Update github templates (lchrusciel)

This PR was merged into the 1.7-dev branch.

Discussion
----------

| Q               | A
| --------------- | -----
| Bug fix?        | yes
| New feature?    | no
| BC breaks?      | no
| Deprecations?   | no
| Related tickets | 
| License         | MIT

I suppose we will not need these fields.

Commits
-------

c923470 [Maintenance] Update gtihub templates

.github/ISSUE_TEMPLATE.md

@@ -4,7 +4,6 @@
 | Feature request? | no/yes
 | BC Break report? | no/yes
 | RFC?             | no/yes
-| Sylius version   | 1.x.y
 
 <!--
  - For support requests and how-tos, visit http://docs.sylius.com/en/latest/support/

.github/PULL_REQUEST_TEMPLATE.md

@@ -1,15 +1,8 @@
 | Q               | A
 | --------------- | -----
-| Branch?         | 1.5, 1.6 or master <!-- see the comment below -->
 | Bug fix?        | no/yes
 | New feature?    | no/yes
 | BC breaks?      | no/yes
 | Deprecations?   | no/yes <!-- don't forget to update the UPGRADE-*.md file -->
 | Related tickets | fixes #X, partially #Y, mentioned in #Z
 | License         | MIT
-
-<!--
- - Bug fixes must be submitted against the 1.5 or 1.6 branch (the lowest possible)
- - Features and deprecations must be submitted against the master branch
- - Make sure that the correct base branch is set
--->