Fix line highlighting in C# and PHP client-level retry examples

Removed blank lines after import statements in C# and PHP client-level
examples to fix line highlighting. The blank lines were causing the
renderer to highlight the wrong line (one line too early).

- C# client-level: Changed from {4} to {3} and removed blank line
- PHP client-level: Changed from {4} to {3} and removed blank line
- Per-request examples were already correct
- Swift examples were already correct

Verified locally with fern docs dev that highlighting now correctly
points to the MaxRetries/maxRetries configuration lines.

Co-Authored-By: Niels Swimberghe <[email protected]>

Author: devin-ai-integration[bot]

fern/products/sdks/guides/retries-with-backoff.mdx

@@ -69,9 +69,8 @@ default retry limit when instantiating the client.
     ```
   </CodeBlock>
   <CodeBlock title="C#">
-    ```csharp {4}
+    ```csharp {3}
     using Imdb;
-
     var client = new ImdbClient(new ClientOptions {
       MaxRetries = 1 // overrides the default retry limit to 1
     });
@@ -88,9 +87,8 @@ default retry limit when instantiating the client.
     ```
   </CodeBlock>
   <CodeBlock title="PHP">
-    ```php {4}
+    ```php {3}
     use Imdb\ImdbClient;
-
     $client = new ImdbClient([
       "maxRetries" => 1 // overrides the default retry limit to 1
     ]);