(Ada) do not print Ada task names in quotes in "info tasks" output

(Ada) do not print Ada task names in quotes in "info tasks" output

A recent change enhanced a couple of notifications about Ada tasks to
include the task's name in addition to the task's number. That change
also modified the output of the "info tasks" when printing the detailed
information of one given task. I believe this change was unintentionally
left over from the initial version after it was decided that quoting
the task's name should not be done. This patch therefore undoes this
part of the patch.

gdb/ChangeLog:

        * ada-tasks.c (info_task): Remove quoting of the task's name.

Tested on x86_64-linux, with both the official testsuite as well as
AdaCore's testsuite.