minor symfony#13236 Consistent spaceless nodes in form templates (peterrehm)

This PR was merged into the 2.3 branch.

Discussion
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Consistent spaceless nodes in form templates

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

Added '-' at the start and at the end of all if, for, set and block nodes. Related to symfony#12422.
Replaces symfony#12560.

Commits
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41c5be6 Added the '-' character for spaceless on tag start and end to be consistent for block, if, set and for nodes

Author: fabpot