[pgAdmin4][PATCH] To handle "char" type in column node

Hi,

PFA minor patch to handle "char" type while creating columns in Column node.

*Issue:* simplejson parse '*"char"*' as valid json, hence when we perform
simplejson.loads(request.args) operation '"char"' gets converted to 'char'
I had to handle it manually as of now, I did not find any other workaround
to handle this issue, I went over several SO question most of them
suggested manual handling.
This behavior is only in Column node, table & type nodes are not affectted
by .loads() method as we send data as column collection.
RM#2152

*Snippet of issue:*
import simplejson as json
print(json.loads('"char"'))

--
Regards,
Murtuza Zabuawala
EnterpriseDB: http://www.enterprisedb.com
The Enterprise PostgreSQL Company