chore(github): use table for Emeritus

- to matches how `argoproj` lists Alumni (https://github.com/argoproj/argoproj/blob/6011d3e17300d4b642a1ab5bdb3551c5f6da9021/MAINTAINERS.md?plain=1#L11)
  - though it has more details including role and affiliation. could do that here too, but I don't know what all those are, so left those columns out
    - fortunately everyone's name was listed on their profile, so just copy+paste those!

- confirmed that all links work

Signed-off-by: Anton Gilgur <agilgur5@gmail.com>

EMERITUS.md

@@ -4,9 +4,11 @@ These are the people who have been approvers in the past, and have since retired
 
 We thank them for their service to the project.
 
-* @oliverbaehler
-* @stefansedich
-* @paguos
-* @yann-soubeyrand
-* @davidkarlsen
-* @jbehling
+| Emeritus | GitHub ID |
+| -------- | --------- |
+| Oliver Bähler | [oliverbaehler](https://github.com/oliverbaehler) |
+| Stefan Sedich | [stefansedich](https://github.com/stefansedich) |
+| Pablo Osinaga | [paguos](https://github.com/paguos) |
+| Yann Soubeyrand | [yann-soubeyrand](https://github.com/yann-soubeyrand) |
+| David J. M. Karlsen | [davidkarlsen](https://github.com/davidkarlsen) |
+| John Behling | [jbehling](https://github.com/jbehling) |