Fix PowerShell Export-ModuleMember error preventing developer mode enablement 15297 (#15306)

* Fix PowerShell Export-ModuleMember error

Rename WindowsStoreAppUtils.ps1 to .psm1 and update reference.
Export-ModuleMember can only be used inside PowerShell modules.

Fixes #15297

* Change files

---------

Co-authored-by: Nitin Chaudhary <nitchaudhary@microsoft.com>

Author: Nitin-100

change/@react-native-windows-cli-b07e800a-e3e5-401f-8510-5cf8c5d4c934.json

@@ -0,0 +1,7 @@
+{
+  "type": "none",
+  "comment": "Fix PowerShell Export-ModuleMember error",
+  "packageName": "@react-native-windows/cli",
+  "email": "nitchaudhary@microsoft.com",
+  "dependentChangeType": "none"
+}

packages/@react-native-windows/cli/src/powershell/WindowsStoreAppUtils.ps1 renamed to packages/@react-native-windows/cli/src/powershell/WindowsStoreAppUtils.psm1

@@ -181,7 +181,7 @@ function getWindowsStoreAppUtils(options: RunWindowsOptions) {
     '..',
     'src',
     'powershell',
-    'WindowsStoreAppUtils.ps1',
+    'WindowsStoreAppUtils.psm1',
   );
   execSync(
     `${powershell} -NoProfile Unblock-File '${windowsStoreAppUtilsPath}'`,