Fix the warnings/errors reported by PHP_CodeSniffer

please review the MR.

Hi @roshni27,

I applied MR!3, it was applied smoothly and fixed most of the phpcs issues.

These are the remaining issues after I ran phpcs --standard=Drupal,DrupalPractice --extensions=php,module,inc,install,test,profile,theme,css,info,txt,md,yml:

➜  field_operations git:(8.x-2.x) curl https://git.drupalcode.org/project/field_operations/-/merge_requests/3.diff | patch -p1
  % Total    % Received % Xferd  Average Speed   Time    Time     Time  Current
                                 Dload  Upload   Total   Spent    Left  Speed
100  2782    0  2782    0     0   6498      0 --:--:-- --:--:-- --:--:--  6515
patching file README.md
patching file field_operations.libraries.yml
patching file field_operations.links.task.yml
patching file field_operations.routing.yml
patching file src/Controller/FieldOperations.php
➜  field_operations git:(8.x-2.x) ✗ ..
➜  contrib phpcs --standard="Drupal,DrupalPractice" --extensions=php,module,inc,install,test,profile,theme,info,txt,md,yml,css,js field_operations

FILE: /Users/interns/Demo-site/drupal-org-issues/web/modules/contrib/field_operations/js/field_operations.js
------------------------------------------------------------------------------------------------------------
FOUND 5 ERRORS AFFECTING 5 LINES
------------------------------------------------------------------------------------------------------------
 16 | ERROR | [x] TRUE, FALSE and NULL must be uppercase; expected "FALSE" but found "false"
 41 | ERROR | [x] TRUE, FALSE and NULL must be uppercase; expected "TRUE" but found "true"
 44 | ERROR | [x] TRUE, FALSE and NULL must be uppercase; expected "TRUE" but found "true"
 46 | ERROR | [x] TRUE, FALSE and NULL must be uppercase; expected "FALSE" but found "false"
 50 | ERROR | [x] TRUE, FALSE and NULL must be uppercase; expected "FALSE" but found "false"
------------------------------------------------------------------------------------------------------------
PHPCBF CAN FIX THE 5 MARKED SNIFF VIOLATIONS AUTOMATICALLY
------------------------------------------------------------------------------------------------------------

Time: 129ms; Memory: 10MB

➜  contrib

Thank you.

MR !3 fixed all the PHP_CodeSniffer errors/warnings reported by GitLab CI.

avpaderno → changed the visibility of the branch 3372384-gitlab-ci-reports to hidden.

avpaderno → changed the visibility of the branch 3372384-fix-the-warningserrors to hidden.

Actually, only a PHP_CodeSniffer error is reported by GitLab CI. The existing merge request fixes PHP_CodeSniffer errors GitLab CI does not report.

MR !6 fixes all the PHP_CodeSniffer errors/warnings reported by GitLab CI.