fix: cleanup unused classes in Notifications and minor code refactoring

[InnaAtanasova]

Related Issue

NA

Description

• removed unused and unnecessary classes
• deleted the rule that removes the border bottom from the last notification in the notification list/group
• added margin for every child inside actions, not only for buttons as we can have a popover
• fixed the RTL rules for the actions

BREAKING CHANGE:

• removed classes: fd-notification__actions--dismiss, fd-notification--tabs and fd-notification__actions--popover

Please check whether the PR fulfills the following requirements

1. The output matches the design specs

• RTL support

2. The code follows fundamental-styles code standards and style
   NA
3. Testing

• Updated tests
• last commit message should have [ci visual] so it can trigger chromatic visual regression (e.g. test: run chromatic visual regression [ci visual])

4. Documentation

• Breaking Changes wiki has been updated in case of breaking changes.

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[droshev]

We are missing show more/less (example).

[droshev]

apart from missing show less/more example everything is good

[InnaAtanasova]

apart from missing show less/more example everything is good

It's not in the scope of this PR. I created a separate issue for this: #2325