Fix incorrect uses of "relationship" instead of "relation" in filtering docs

[bradjones1]

This cost me a few minutes of head-scratching today.

See

orbit/packages/@orbit/records/src/record-query-term.ts

Lines 45 to 91 in d0fb7cd

	export interface RelatedRecordFilterParam<RI = RecordIdentity> {
	op?: SetComparisonOperator;
	relation: string;
	record: RI | RI[] | null;
	}
	export interface RelatedRecordsFilterParam<RI = RecordIdentity> {
	op?: SetComparisonOperator;
	relation: string;
	records: RI[];
	}
	export type FilterParam<RI = RecordIdentity> =
	| FilterSpecifier
	| AttributeFilterParam
	| RelatedRecordFilterParam<RI>
	| RelatedRecordsFilterParam<RI>;
	function isFilterSpecifier<RI = RecordIdentity>(
	param: FilterParam<RI>
	): param is FilterSpecifier {
	return (param as FilterSpecifier).kind !== undefined;
	}
	function isAttributeFilterParam<RI = RecordIdentity>(
	param: FilterParam<RI>
	): param is AttributeFilterParam {
	return (param as AttributeFilterParam).attribute !== undefined;
	}
	function isRelatedRecordFilterParam<RI = RecordIdentity>(
	param: FilterParam<RI>
	): param is RelatedRecordFilterParam<RI> {
	return (
	(param as RelatedRecordFilterParam<RI>).relation !== undefined &&
	(param as RelatedRecordFilterParam<RI>).record !== undefined
	);
	}
	function isRelatedRecordsFilterParam<RI = RecordIdentity>(
	param: FilterParam<RI>
	): param is RelatedRecordsFilterParam<RI> {
	return (
	(param as RelatedRecordsFilterParam<RI>).relation !== undefined &&
	(param as RelatedRecordsFilterParam<RI>).records !== undefined
	);
	}

[dgeb]

@bradjones1 thanks for the correction and sorry for the confusion!