fix(collapse): fix setting display value

[SvetlanaMuravlova]

fix(collapse): fix setting display value
refs #6070 refs #6071

[github-actions]

Visit the preview URL for this PR (updated for commit c702e0e):

https://ngx-bootstrap-demo--pr6257-fix-collapse-display-k2ocsxxd.web.app

_{(expires Mon, 13 Sep 2021 14:34:17 GMT)}

_{🔥 via Firebase Hosting GitHub Action 🌎}

[codecov]

Codecov Report

Merging #6257 (64bb7d8) into development (6c138db) will increase coverage by 0.02%.
The diff coverage is 0.00%.

❗ Current head 64bb7d8 differs from pull request most recent head c702e0e. Consider uploading reports for the commit c702e0e to get more accurate results

@@               Coverage Diff               @@
##           development    #6257      +/-   ##
===============================================
+ Coverage        77.24%   77.27%   +0.02%     
===============================================
  Files              311      311              
  Lines            10681    10678       -3     
  Branches          2625     2625              
===============================================
  Hits              8251     8251              
+ Misses            2420     2417       -3     
  Partials            10       10              

Impacted Files	Coverage Δ
src/collapse/collapse.directive.ts	73.86% <0.00%> (+2.43%)	⬆️

---

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 6c138db...c702e0e. Read the comment docs.

[cypress]

---

Test summary

87 • 0 • 6 • 0

---

Run details

Project	ngx-bootstrap
Status	Passed
Commit	64bb7d8 ℹ️
Started	Sep 6, 2021 2:35 PM
Ended	Sep 6, 2021 2:40 PM
Duration	05:07 💡
OS	Linux Ubuntu - 20.04
Browser	Electron 87

View run in Cypress Dashboard ➡️

---

This comment has been generated by cypress-bot as a result of this project's GitHub integration settings. You can manage this integration in this project's settings in the Cypress Dashboard