docs: Remove 'specify property field type' part from new feature tutorial.
docs: Remove 'specify property field type' part from new feature tutorial.

This commit removes the part which mentions specifying the property field
type in new feauture tutorial as it is no longer required to specify the
type.

zulip/zulip,kou/zulip,eeshangarg/zulip,punchagan/zulip,eeshangarg/zulip,hackerkid/zulip,kou/zulip,andersk/zulip,punchagan/zulip,punchagan/zulip,rht/zulip,rht/zulip,hackerkid/zulip,punchagan/zulip,hackerkid/zulip,showell/zulip,showell/zulip,andersk/zulip,zulip/zulip,rht/zulip,showell/zulip,eeshangarg/zulip,zulip/zulip,andersk/zulip,kou/zulip,punchagan/zulip,andersk/zulip,zulip/zulip,rht/zulip,kou/zulip,punchagan/zulip,kou/zulip,rht/zulip,eeshangarg/zulip,hackerkid/zulip,kou/zulip,andersk/zulip,rht/zulip,hackerkid/zulip,eeshangarg/zulip,kou/zulip,rht/zulip,zulip/zulip,andersk/zulip,showell/zulip,showell/zulip,zulip/zulip,zulip/zulip,andersk/zulip,eeshangarg/zulip,showell/zulip,hackerkid/zulip,hackerkid/zulip,punchagan/zulip,showell/zulip,eeshangarg/zulip