minor symfony#24328 Use correct verb form in the pull request template (pamil)

This PR was merged into the 2.7 branch.

Discussion
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Use correct verb form in the pull request template

| Q             | A
| ------------- | ---
| Branch?       | 2.7
| Bug fix?      | no
| New feature?  | no
| BC breaks?    | no
| Deprecations? | no
| Tests pass?   | yes
| Fixed tickets | -
| License       | MIT
| Doc PR        | -

When "forget" is used with a gerund, it refers to an action that has already happened.

Commits
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484e3fd Use correct verb form in the pull request template

Author: stof

.github/PULL_REQUEST_TEMPLATE.md

@@ -2,9 +2,9 @@
 | ------------- | ---
 | Branch?       | 3.4 or master / 2.7, 2.8 or 3.3 <!-- see comment below -->
 | Bug fix?      | yes/no
-| New feature?  | yes/no <!-- don't forget updating src/**/CHANGELOG.md files -->
+| New feature?  | yes/no <!-- don't forget to update src/**/CHANGELOG.md files -->
 | BC breaks?    | yes/no
-| Deprecations? | yes/no <!-- don't forget updating UPGRADE-*.md files -->
+| Deprecations? | yes/no <!-- don't forget to update UPGRADE-*.md files -->
 | Tests pass?   | yes/no
 | Fixed tickets | #... <!-- #-prefixed issue number(s), if any -->
 | License       | MIT