fix(GlSearchBox*): Hide Chrome's cancel button

What does this MR do?

Since !2492 (merged), the GlSearchBoxByType and GlSearchBoxByClick components have shown a blue cancel button when text is entered into the inputs.

Since we already add our own custom cancel/clear button to the input, this browser-provided one needs to be hidden.

See https://developer.mozilla.org/en-US/docs/Web/CSS/::-webkit-search-cancel-button.

Screenshots

Before	After

Does this MR meet the acceptance criteria?

Conformity

• Code review guidelines.
• GitLab UI's contributing guidlines.
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• Added the ~"component:*" label(s) if applicable.

Security

If this MR contains changes to processing or storing of credentials or tokens, authorization and authentication methods and other items described in the security review guidelines:

• [-] Label as security and @ mention @gitlab-com/gl-security/appsec
• [-] Security reports checked/validated by a reviewer from the AppSec team

Accessibility

If this MR adds or modifies a component, take a few moments to review the following:

• [-] All actions and functionality can be done with a keyboard.
• [-] Links, buttons, and controls have a visible focus state.
• [-] All content is presented in text or with a text equivalent. For example, alt text for SVG, or aria-label for icons that have meaning or perform actions.
• [-] Changes in a component’s state are announced by a screen reader. For example, changing aria-expanded="false" to aria-expanded="true" when an accordion is expanded.
• [-] Color combinations have sufficient contrast.