search suggestions: Refactor `get_default_suggestion`.
search suggestions: Refactor `get_default_suggestion`.

This commit actually just deletes the `get_default_suggestion`
function while the `get_default_suggestion_legacy` function's
logic remains the exact same, it is just renamed.

Since the operator can never be undefined as mentioned in the
previous commit, we do not require the check with undefined
and as a result the, `if (suggestion)` condition can be removed.

eeshangarg/zulip,hackerkid/zulip,shubhamdhama/zulip,timabbott/zulip,kou/zulip,rht/zulip,showell/zulip,rht/zulip,hackerkid/zulip,kou/zulip,brainwane/zulip,eeshangarg/zulip,zulip/zulip,andersk/zulip,hackerkid/zulip,brainwane/zulip,brainwane/zulip,kou/zulip,timabbott/zulip,rht/zulip,timabbott/zulip,punchagan/zulip,shubhamdhama/zulip,synicalsyntax/zulip,eeshangarg/zulip,synicalsyntax/zulip,hackerkid/zulip,showell/zulip,brainwane/zulip,showell/zulip,hackerkid/zulip,andersk/zulip,synicalsyntax/zulip,punchagan/zulip,timabbott/zulip,showell/zulip,eeshangarg/zulip,shubhamdhama/zulip,rht/zulip,shubhamdhama/zulip,kou/zulip,rht/zulip,brainwane/zulip,punchagan/zulip,eeshangarg/zulip,hackerkid/zulip,rht/zulip,timabbott/zulip,shubhamdhama/zulip,kou/zulip,andersk/zulip,eeshangarg/zulip,showell/zulip,brainwane/zulip,brainwane/zulip,synicalsyntax/zulip,andersk/zulip,shubhamdhama/zulip,punchagan/zulip,timabbott/zulip,kou/zulip,zulip/zulip,synicalsyntax/zulip,zulip/zulip,synicalsyntax/zulip,kou/zulip,showell/zulip,synicalsyntax/zulip,zulip/zulip,zulip/zulip,hackerkid/zulip,punchagan/zulip,zulip/zulip,rht/zulip,andersk/zulip,punchagan/zulip,andersk/zulip,andersk/zulip,showell/zulip,eeshangarg/zulip,timabbott/zulip,zulip/zulip,punchagan/zulip,shubhamdhama/zulip