[Security Solution] Update insight depth limit to 1 (elastic#161901)

## Summary

Before elastic#160691 was merged, the
filter builder depth of 1 was the same as 0, and so I mistakenly had
this value set to 2. With it set to 2, it's possible to create a filter
with top level AND and 2 levels of nesting that will cause the designed
for only 1 level of nesting data provider code to throw a run time
error. Setting this to the now working level of 1 prevents that.

(cherry picked from commit 97705ff)

x-pack/plugins/security_solution/public/common/components/markdown_editor/plugins/insight/index.tsx

@@ -485,7 +485,7 @@ const InsightEditorComponent = ({
                   filters={filtersStub}
                   onChange={onChange}
                   dataView={dataView}
-                  maxDepth={2}
+                  maxDepth={1}
                 />
               ) : (
                 <></>