refactor(magnification): Rename enableWindowMagnificationInternal for better readability

Renaming `enableWindowMagnificationInternal` to
`updateWindowMagnificationInternal` since this mathod is used in both
enabling and deleting window magnification when we perform zoom in/out
animation. Changing the name to `update` could help us improve the
readability for the codebase.

Bug: 323528222
Test: atest WindowMagnificationControllerTest
      atest WindowMagnificationControllerWindowlessMagnifierTest
      atest WindowMagnificationAnimationControllerTest
Flag: N/A
Change-Id: I791eebb884ca345be5770741014e17c34bbfb542