Add automatic optimization property setter to lightning module

[ananthsub]

What does this PR do?

This speeds up the deprecation of the automatic_optimization flag from the Trainer by making this property settable on the module. So someone could do self.automatic_optimization = False without running into an attribute error

Fixes # (issue)

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[rohitgr7]

this looks better to me. Mind update other tests too?

[awaelchli]

I thought it already was like this 😄

[ananthsub]

this looks better to me. Mind update other tests too?

will do!

[codecov]

Codecov Report

Merging #5169 (bb42800) into master (92bbf2f) will increase coverage by 0%.
The diff coverage is 100%.

@@          Coverage Diff           @@
##           master   #5169   +/-   ##
======================================
  Coverage      93%     93%           
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  Files         135     135           
  Lines       10011   10015    +4     
======================================
+ Hits         9324    9328    +4     
  Misses        687     687