Update codeowners of /src/solvers/smt2 to those working on it

Removing @allredj @romainbrenguier as these people do not currently work
on SMT2 support. Adding @thomasspriggs @NlightNFotis @TGWDB due to
current experience of working on SMT2 support.

Author: thomasspriggs

CODEOWNERS

@@ -54,7 +54,7 @@
 /jbmc/src/janalyzer/ @peterschrammel @romainbrenguier
 /jbmc/src/jdiff/ @peterschrammel
 /src/cpp/ @kroening @tautschnig @peterschrammel
-/src/solvers/smt2 @kroening @martin-cs @peterschrammel @allredj @romainbrenguier
+/src/solvers/smt2 @kroening @martin-cs @peterschrammel @thomasspriggs @NlightNFotis @TGWDB
 /src/solvers/smt2_incremental @peterschrammel @thomasspriggs @NlightNFotis @TGWDB @chrisr-diffblue
 /src/statement-list/ @kroening @tautschnig @peterschrammel @pkesseli