refactor: start on removing FF for subscription tiers (#7596)

## Summary

Refactor: remove FF for subscription tier, remove legacy code for non
subscription tier logic.
 
## Review Focus

Preexisting cloud functionality impact.

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<!-- Fixes #ISSUE_NUMBER -->

## Screenshots (if applicable)

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┆Issue is synchronized with this [Notion
page](https://www.notion.so/PR-7596-refactor-start-on-removing-FF-for-subscription-tiers-2cc6d73d3650816bac3aef893e4f37cd)
by [Unito](https://www.unito.io)

src/platform/settings/composables/useSettingUI.ts

@@ -3,7 +3,6 @@ import type { Component } from 'vue'
 import { useI18n } from 'vue-i18n'
 
 import { useCurrentUser } from '@/composables/auth/useCurrentUser'
-import { useFeatureFlags } from '@/composables/useFeatureFlags'
 import { isCloud } from '@/platform/distribution/types'
 import type { SettingTreeNode } from '@/platform/settings/settingStore'
 import { useSettingStore } from '@/platform/settings/settingStore'
@@ -36,7 +35,6 @@ export function useSettingUI(
 
   const { shouldRenderVueNodes } = useVueFeatureFlags()
   const { isActiveSubscription } = useSubscription()
-  const { flags } = useFeatureFlags()
 
   const settingRoot = computed<SettingTreeNode>(() => {
     const root = buildTree(
@@ -106,7 +104,6 @@ export function useSettingUI(
 
   const shouldShowPlanCreditsPanel = computed(() => {
     if (!subscriptionPanel) return false
-    if (!flags.subscriptionTiersEnabled) return true
     return isActiveSubscription.value
   })