minor #31583 [github] define 4.4 as the feature branch (nicolas-grekas)

This PR was merged into the 3.4 branch.

Discussion
----------

[github] define 4.4 as the feature branch

| Q             | A
| ------------- | ---
| Branch?       | 3.4
| Bug fix?      | no
| New feature?  | no
| BC breaks?    | no
| Deprecations? | no
| Tests pass?   | yes
| Fixed tickets | -
| License       | MIT
| Doc PR        | -

And let's use master for preparing 5.0.

Commits
-------

30b560c4df [github] define 4.4 as the feature branch

.github/PULL_REQUEST_TEMPLATE.md

@@ -1,6 +1,6 @@
 | Q             | A
 | ------------- | ---
-| Branch?       | master for features / 3.4, 4.2 or 4.3 for bug fixes <!-- see below -->
+| Branch?       | 4.4 for features / 3.4, 4.2 or 4.3 for bug fixes <!-- see below -->
 | Bug fix?      | yes/no
 | New feature?  | yes/no <!-- please update src/**/CHANGELOG.md files -->
 | BC breaks?    | no     <!-- see https://symfony.com/bc -->
@@ -17,5 +17,6 @@ understand your PR and can be used as a start for the documentation.
 Additionally (see https://symfony.com/roadmap):
  - Bug fixes must be submitted against the lowest maintained branch where they apply
    (lowest branches are regularly merged to upper ones so they get the fixes too).
- - Features and deprecations must be submitted against the master branch.
+ - Features and deprecations must be submitted against branch 4.4.
+ - Legacy code removals go to the master branch.
 -->