Remove whereBuilder

[yurishkuro]

I was browsing the code and noticed this stuct. It does not seem to be used, so I recommend removing it because it is vulnerable to SQL injection:

jaeger-postgresql/pgstore/mapping.go

Lines 5 to 16 in b648037

	type whereBuilder struct {
	where string
	params []interface{}
	}
	func (r *whereBuilder) andWhere(param interface{}, where string) {
	if len(r.where) > 0 {
	r.where += " AND "
	}
	r.where += where
	r.params = append(r.params, param)
	}