Revert attention_layer.hpp formatting change

CI uses clang-format-16 which prefers the previous indentation; my local
clang-format-20 reformatted it differently.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

Author: Dobiasd

include/fdeep/layers/attention_layer.hpp

@@ -34,7 +34,7 @@ namespace internal {
             const tensor& value = input[1];
             const tensor& key = input.size() > 2 ? input[2] : value;
             const tensor scores = score_mode_ == "dot" ? transform_tensor(fplus::multiply_with(scale_),
-                                                             dot_product_tensors(query, transpose(key), std::vector<int>({ 2, 1 }), false))
+                                      dot_product_tensors(query, transpose(key), std::vector<int>({ 2, 1 }), false))
                                                        :
                                                        // https://github.com/keras-team/keras/blob/v2.13.1/keras/layers/attention/attention.py
                 transform_tensor(fplus::multiply_with(concat_score_weight_),