Move designer bio to correct location (#6293)

* Move vietanhnguyen designer bio to expected file location

* Update to_sandbox.txt with expected designer bio path

to_sandbox.txt

@@ -4,7 +4,7 @@ ofl/notoserif # https://github.com/google/fonts/pull/6134
 
 # Designer profile
 catalog/designers/suonmaysophanith # https://github.com/google/fonts/pull/6256
-catalog/vietanhnguyen # https://github.com/google/fonts/pull/6254
+catalog/designers/vietanhnguyen # https://github.com/google/fonts/pull/6254
 
 # Metadata / Description / License
 ofl/poltawskinowy # https://github.com/google/fonts/pull/6280