runqemu: refactor a duplicated cleanup statement

Refactor using a "finally:" instead of a duplicated statement inside and
outside of the try/except block.

(From OE-Core rev: c92399c355d1333eff37ea799832a8890acd0d74)

Signed-off-by: Yoann Congal <yoann.congal@smile.fr>
Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>

scripts/runqemu

@@ -450,11 +450,10 @@ class BaseConfig(object):
             try:
                 subprocess.check_call(['zstd', '-d', image_path, '-o', uncompressed_path])
             except subprocess.CalledProcessError as e:
-                self.cleanup_files.append(uncompressed_path)
                 raise RunQemuError(f"Failed to decompress {self.rootfs}: {e}")
-    
-            # Mark for deletion at the end
-            self.cleanup_files.append(uncompressed_path)
+            finally:
+                # Mark temporary file for deletion
+                self.cleanup_files.append(uncompressed_path)
     
         # Use the decompressed image as the rootfs
         self.rootfs = uncompressed_path