remove presentation for ECSA 21 until disappeared from Google Scholar (re-add afterward)

Author: dfuchss

_conferences/ecsa21.md

@@ -37,4 +37,4 @@ Moreover, our approach outperforms the baseline approaches on non-weighted avera
 
 - Paper on [Springer Link](https://doi.org/10.1007/978-3-030-86044-8_7) and on [KITopen](https://doi.org/10.5445/IR/1000138399)
 - Replication Package on [Zenodo](https://doi.org/10.5281/zenodo.4730621) and the corresponding [GitHub repository](https://github.com/ardoco/SWATTR)
-- [Slides](/assets/pdf/presentation_21_ecsa_TLR.pdf)
+<!-- - [Slides](/assets/pdf/presentation_21_ecsa_TLR.pdf) -->