fixed image alignment, side by side not possible

ETS_theory.asciidoc

@@ -39,6 +39,7 @@ For example, if the oscilloscope captures in ETS mode and the user disables the
 [.center]
 image::https://es.technikum-wien.at/openlab/openlab_wiki/wikis/img/ETS_theory/ETS_glitch.png[caption="Figure 1: ",title="Non-repititive signal captured using ETS (3)",height=300]
 
+{empty} +
 {empty} +
 
 [.center]