Deprecate the popover style file

app/assets/stylesheets/components/popover.scss

-.popover {
-  max-width: $popover-max-width;
-  border: 1px solid $gray-100;
-  box-shadow: $popover-box-shadow;
-  font-size: $gl-font-size-small;
-
-  /**
-  * Blue popover variation
-  */
-  &.blue {
-    background-color: $blue-600;
-    border-color: $blue-600;
-
-    .popover-body {
-      color: $white;
-    }
-
-    &.bs-popover-bottom {
-      .arrow::before,
-      .arrow::after {
-        border-bottom-color: $blue-600;
-      }
-    }
-
-    &.bs-popover-top {
-      .arrow::before,
-      .arrow::after {
-        border-top-color: $blue-600;
-      }
-    }
-
-    &.bs-popover-right {
-      .arrow::after,
-      .arrow::before {
-        border-right-color: $blue-600;
-      }
-    }
-
-    &.bs-popover-left {
-      .arrow::before,
-      .arrow::after {
-        border-left-color: $blue-600;
-      }
-    }
-  }
-}
-
-.bs-popover-top {
-  /* When popover position is top, the arrow is translated 1 pixel
-  *  due to the box-shadow include in our custom styles.
-  */
-  > .arrow::before {
-    border-top-color: $gray-100;
-    bottom: 1px;
-  }
-
-  > .arrow::after {
-    bottom: 2px;
-  }
-}
-
-.bs-popover-bottom {
-  > .arrow::before {
-    border-bottom-color: $gray-100;
-  }
-
-  > .popover-header::before {
-    border-color: $white;
-  }
-}
-
-.bs-popover-right > .arrow::before {
-  border-right-color: $gray-100;
-}
-
-.bs-popover-left > .arrow::before {
-  border-left-color: $gray-100;
-}
-
-.popover-header {
-  background-color: $white;
-  font-size: $gl-font-size-small;
-}
-
-.popover-body {
-  padding: $gl-padding $gl-padding-12;
-
-  > .popover-hr {
-    margin: $gl-padding 0;
-  }
-}
-
-/**
-* mr_popover component
-*/
-.mr-popover {
-  .text-secondary {
-    font-size: 12px;
-    line-height: 1.33;
-  }
-}
-
-.suggest-gitlab-ci-yml {
-  margin-top: -1em;
-
-  .popover-header {
-    padding: $gl-padding;
-    display: flex;
-    align-items: center;
-  }
-}