ChooseLockPattern: remove redundant setting of visible pattern default

Remove the code that set LOCK_PATTERN_VISIBLE to true the first time a
pattern was set, since LOCK_PATTERN_VISIBLE now defaults to true when
unset (ag/22912136).  The explicit defaulting to true was only needed
before because the low-level default value was wrong.

Bug: 270013005
Test: Set a pattern.  Verified that Keyguard uses visible pattern.
      Disabled the "Make pattern visible" option in Settings.  Verified
      that Keyguard doesn't use visible pattern.
Change-Id: I63f29c68f9a508fee0ee2f03f2cca33317fb8a32
Merged-In: I63f29c68f9a508fee0ee2f03f2cca33317fb8a32
(cherry picked from commit 6c3de300)