drop support for Ember Bootstrap v4

Author: jelhan

.github/workflows/ci.yml

@@ -67,7 +67,6 @@ jobs:
           - ember-canary
           - ember-default-with-jquery
           - ember-classic
-          - ember-bootstrap-v4
           - ember-power-select-v4
     steps:
       - name: Checkout code

README.md

@@ -11,7 +11,7 @@ Compatibility
 ------------------------------------------------------------------------------
 
 * Ember Power Select v4 or above
-* Ember Bootstrap v4 or above
+* Ember Bootstrap v5 or above
 * Ember.js v3.16 or above
 * Ember CLI v3.16 or above
 * Node.js v12 or above

config/ember-try.js

@@ -106,17 +106,6 @@ module.exports = async function () {
       },
       embroiderSafe(),
       embroiderOptimized(),
-      {
-        name: 'ember-bootstrap-v4',
-        npm: {
-          devDependencies: {
-            'ember-bootstrap': '^4.9.0',
-          },
-          resolutions: {
-            '@embroider/macros': '^0.50.2',
-          },
-        },
-      },
       {
         name: 'ember-power-select-v4',
         npm: {