Drop pinner.pin_camera=false from the default prop.

The pin_camera flag being false makes some in-market devices
(redfin, bramble, coral, etc.) not pin the camera app by default.
Although a Phenotype flag overrides this value,
the OTA flag delivery can fail and ends up non-ping state.

This change makes sure that the device pins the camera app by default
by removing pinner.pin_camera properties modification from this file.
The current default is to pin the camera. See PinnerServices.java

Note that the camera pinning is still disabled on crosshatch family,
sicne it is known to be prone to the memory shortage.
See device-crosshatch.mk.

Also note that some newer devices already pin by default because
they don't refer this file, although the name implies it might.

Test: On Redfin:
  $ vendor/google/tools/flashall -w
  $ adb root && adb wait-for-device && adb shell am start -a com.android.setupwizard.FOUR_CORNER_EXIT
  $ adb shell dumpsys pinner
Bug: 195035033
Bug: 184897981
Merged-In: I81207d0527f758d4800319a3a3c323919daaf814
Change-Id: I81207d0527f758d4800319a3a3c323919daaf814