Remove branches constraint from .drone.yml

[dschmidt]

We want to upgrade drone.owncloud.com to Drone 1.x. The branches settings are not correctly converted automatically and @tboerger and I discussed multiple options how to deal with it:

1. "Fix" the conversion tool Cumbersome and there's no perfect solution that would satisfy all users of drone.
2. Port all repos to the new drone 1.x config, possibly using jsonnet A lot of work if not done completely naively, high chance of breaking things.
3. Simply remove the condition (what this PR does) Fairly easy with only one downside: duplicated builds: If a PR is sent from a branch in this repository, we see duplicated builds for the branch AND the PR. This will of course be fixed when we move to the newer syntax over time.

A PR is created automatically for all apps bundled with core according to @tboerger and @PVince81. If this repository does not need a PR for master or an additional PR for a separate branch, let me know in the discussion.

[codecov[bot]]

Codecov Report

Merging #120 into master will not change coverage. The diff coverage is n/a.

@@            Coverage Diff            @@
##             master     #120   +/-   ##
=========================================
  Coverage     64.68%   64.68%           
  Complexity       61       61           
=========================================
  Files            13       13           
  Lines           252      252           
=========================================
  Hits            163      163           
  Misses           89       89

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Continue to review full report at Codecov.

Legend - Click here to learn more Δ = absolute <relative> (impact), ø = not affected, ? = missing data Powered by Codecov. Last update 37fb426...b0e7a09. Read the comment docs.

[codecov[bot]]

Codecov Report

Merging #120 into master will not change coverage. The diff coverage is n/a.

@@            Coverage Diff            @@
##             master     #120   +/-   ##
=========================================
  Coverage     64.68%   64.68%           
  Complexity       61       61           
=========================================
  Files            13       13           
  Lines           252      252           
=========================================
  Hits            163      163           
  Misses           89       89

---

Continue to review full report at Codecov.

Legend - Click here to learn more Δ = absolute <relative> (impact), ø = not affected, ? = missing data Powered by Codecov. Last update 37fb426...b0e7a09. Read the comment docs.