[BD-9310][BpkMobileScrollContainer] Remove unused scroll indicators

[giriawu]

BD-9310

We are looking for the reason why the BpkMobileScrollContainer component triggers client crash in iOS Safari 15.x.
In the last PR we converted the jsx file to a stable tsx file and fixed some possible bugs, but the client crash still happened when we tried to upgrade to the latest BpkMobileScrollContainer component within the hotels-website.
We suspected that a potentially problematic scss file was introduced in the scss packaging file, and raised this PR to remove unused scroll-indicators in BpkMobileScrollContainer.module.css

Have tested in the storybook, won't affect original scroll feature.

Remember to include the following changes:

• Ensure the PR title includes the name of the component you are changing so it's clear in the release notes for consumers of the changes in the version e.g [KOA-123][BpkButton] Updating the colour
• README.md (If you have created a new component)
• Component README.md
• Tests
• Accessibility tests
  • The following checks were performed:
    • Ability to navigate using a keyboard only
    • Zoom functionality (Deque University explanation):
      • The page SHOULD be functional AND readable when only the text is magnified to 200% of its initial size
      • Pages must reflow as zoom increases up to 400% so that content continues to be presented in only one column i.e. Content MUST NOT require scrolling in two directions (both vertically and horizontally)
    • Ability to navigate using a screen reader only
• Storybook examples created/updated
• For breaking changes or deprecating components/properties, migration guides added to the description of the PR. If the guide has large changes, consider creating a new Markdown page inside the component's docs folder and link it here

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