DOC: Add TableExpr.drop to API documentation
DOC: Add TableExpr.drop to API documentation

Closes #1644

Author: Phillip Cloud <cpcloud@gmail.com>

Closes #1645 from cpcloud/doc-table-drop and squashes the following commits:

8fb35b6 [Phillip Cloud] DOC: Add TableExpr.drop to API documentation

cpcloud/ibis,cpcloud/ibis,ibis-project/ibis,cpcloud/ibis,ibis-project/ibis,cpcloud/ibis,cloudera/ibis,ibis-project/ibis,cloudera/ibis,cloudera/ibis,ibis-project/ibis