[Clean Fluid API]Remove API: unsqueeze, use paddle.unsqueeze to replace paddle.fluid.layers.unsqueeze (#47936)

* Remove API: unsqueeze
	Replace the funcation call.
	Use paddle.unsqueeze to replace paddle.fluid.layers.unsqueeze

* Remove API: unsqueeze
	remove unsqueeze which is not used in Paddle 2.0

* Remove API: unsqueeze
	fix the bug by adding 'import paddle' to file
tests/unittests/test_rnn_cell_api.py

* Modify the call of unsqueeze from old style to new style

* fix the call arguments of unsqueeze

* replace unqueeze with paddle.unsqueeze

* fix the error in PR-CI-Static-Check, name 'paddle' is not defined

* fix the error in static in unsqueeze