Fix: TypeError Invalid URL error in prepareBaseUrl (#8470)

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## Purpose
_Describe the problem you want to address or the feature you want to
implement._

## Approach
_Describe how your changes address the issue or implement the desired
functionality in as much detail as possible._

## References
closes #8434
closes #8364

## Pre-Merge TODO
- [ ] Write tests for your proposed changes
- [ ] Make sure that existing tests do not fail

---------

Co-authored-by: adil.rakhaliyev <[email protected]>

Author: Bayheck

src/api/test-page-url.ts

@@ -3,7 +3,6 @@ import OS from 'os-family';
 import { APIError } from '../errors/runtime';
 import { RUNTIME_ERRORS } from '../errors/types';
 import { SPECIAL_BLANK_PAGE } from 'testcafe-hammerhead';
-import { join } from 'path';
 
 const PROTOCOL_RE           = /^([\w-]+?)(?=:\/\/)/;
 const SUPPORTED_PROTOCOL_RE = /^(https?|file):/;
@@ -51,7 +50,9 @@ export function getUrl (url: string, base?: URL): string {
 }
 
 export function prepareBaseUrl (url: string): URL {
-    url = join(url, '/');
+    if (!url.endsWith('/'))
+        url += '/';
+
     return isAbsolute(url) ? pathToFileURL(url) : new URL(url);
 }