Remove windowMode from nb-layout by set windowMode=false doesn't take effect

### Issue type

**I'm submitting a ...** (check one with "x")

* [x] bug report
* [ ] feature request

### Issue description

**Current behavior:**
Remove windowMode from nb-layout by set windowMode=false doesn't take effect

**Expected behavior:**
The page should occupy the whole browser view area.

**Steps to reproduce:**
Write a component with nb-layout, set windowMode to false.

**Related code:**

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### Other information:

**npm, node, OS, Browser**
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**Angular, Nebular**
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