README: refer to documents in Gitlab pages instead of the build artifacts

The latter worked before... but easily become broken with changes of
Gitlab's configuration/version.

README.md

@@ -35,10 +35,10 @@ Much of FIJI's documentation gets automatically built with every relevant commit
 
 The following documents are available:
 
- - [User Guide](https://es.technikum-wien.at/vecs/fiji_public/builds/artifacts/master/file/docs/fiji_user_guide.pdf?job=build-latex) ([PDF](https://es.technikum-wien.at/vecs/fiji_public/builds/artifacts/master/raw/docs/fiji_user_guide.pdf?job=build-latex))
+ - [User Guide (PDF)](https://es.technikum-wien.at/pages/vecs/fiji_public/fiji_user_guide.pdf)
 
     Explains everything a user of FIJI should have to care about.
- - [Technical Reference Manual](https://es.technikum-wien.at/vecs/fiji_public/builds/artifacts/master/file/docs/fiji_trm.pdf?job=build-latex) ([PDF](https://es.technikum-wien.at/vecs/fiji_public/builds/artifacts/master/raw/docs/fiji_trm.pdf?job=build-latex))
+ - [Technical Reference Manual (PDF)](https://es.technikum-wien.at/pages/vecs/fiji_public/fiji_trm.pdf)
 
     The target audience of this documents are engineers that want to understand or tinker with the inner workings of the FIJI suite.
     The technical details contained herein are supposed to be irrelevant to ordinary users.
@@ -55,7 +55,7 @@ A proper P&R tool for the respective FPGA has to be installed as well to produce
 Our toolchain itself does only need Perl and some associated libraries.
 However, for the example work flow in `docs/demos/*` the `make` utility and a number of common Unix programs are required.
 Building the various forms of [documentation](#documentation) need Latex and Doxygen facilities to be available as well.
-Please see the [User Guide](https://es.technikum-wien.at/vecs/fiji_public/builds/artifacts/master/file/docs/fiji_user_guide.pdf?job=build-latex) for more details.
+Please see the [User Guide (PDF)](https://es.technikum-wien.at/pages/vecs/fiji_public/fiji_user_guide.pdf) for more details.
 
 > **Attention:**
 The upstream version of `Verilog::Perl` (`Verilog::Language`) does support the required features since the 3.442 release.