Update assistResFellow positions

Author: micskeiz

src/content/members/active.yml

@@ -113,7 +113,7 @@
   linkedInPage: https://www.linkedin.com/in/k-marussy
 - firstName: Mihály
   lastName: Dobos-Kovács
-  position: phdStudent
+  position: assistResFellow
   avatar: ../images/members/dobos-kovacs.jpg
   homePage: dobos
   mtmtPage: https://m2.mtmt.hu/gui2/?type=authors&mode=browse&sel=10073065
@@ -151,15 +151,15 @@
   githubPage: https://github.com/grbeni
 - firstName: Richárd
   lastName: Szabó
-  position: phdStudent
+  position: assistResFellow
   avatar: ../images/members/szabo.jpg
   homePage: szabo
   cvPage: https://rorck.github.io/files/richard_szabo_cv.pdf
   mtmtPage: https://m2.mtmt.hu/gui2/?type=authors&mode=browse&sel=10068607
   linkedInPage: https://www.linkedin.com/in/rich%C3%A1rd-szab%C3%B3-037450230/
 - firstName: Dániel
   lastName: Szekeres
-  position: phdStudent
+  position: assistResFellow
   avatar: ../images/members/szekeres.png
   homePage: szekeres
   cvPage: https://szdan97.github.io/cv_szekeres.pdf