Correct case of blazor.webassembly.js paths

- how did Linux builds ever work?
  - case difference between these lines and global `$(Configuration)` value is **really** old
  - same for case in src/Components/Web.JS/src/webpack.config.js versus `$(Configuration)`

I'm not sure this is the right fix when building `Debug`
- will overwrite the checked-in dist/Debug files
- should the project no-op in that configuration?

Error seen in #21487 w/o this:
``` text
error MSB3954: Failed to compute hash for file '/datadisks/disk1/workspace/_work/1/s/src/Components/Web.JS/dist/Release/blazor.webassembly.js' because it does not exist or is inaccessible.
```

Author: dougbu

src/Components/Web.JS/Microsoft.AspNetCore.Components.Web.JS.npmproj

@@ -7,8 +7,8 @@
   </PropertyGroup>
 
   <ItemGroup>
-    <BuildOutputFiles Include="dist\release\blazor.server.js" />
-    <BuildOutputFiles Include="dist\release\blazor.webassembly.js" />
+    <BuildOutputFiles Include="dist\$(Configuration)\blazor.server.js" />
+    <BuildOutputFiles Include="dist\$(Configuration)\blazor.webassembly.js" />
   </ItemGroup>
 
   <ItemGroup>