Rename --no-mirror to --no-playback

This option impacts video and audio _playback_. For example, if we use
V4L2, the device is still "mirrored" (via V4L2), even if playback is
disabled. Therefore, "playback" is more approriate than "mirror".

The initial option --no-display option was renamed to --no-mirror by
commit 6928acdeac, but this has never been
released, so it is ok to rename it one more time.

Refs #3978 <https://github.com/Genymobile/scrcpy/pull/3978#issuecomment-1549420103>
PR #4033 <https://github.com/Genymobile/scrcpy/pull/4033>

app/data/zsh-completion/_scrcpy

@@ -39,7 +39,7 @@ arguments=(
     '--no-clipboard-autosync[Disable automatic clipboard synchronization]'
     '--no-downsize-on-error[Disable lowering definition on MediaCodec error]'
     {-n,--no-control}'[Disable device control \(mirror the device in read only\)]'
-    {-N,--no-mirror}'[Do not mirror device \(only when recording or V4L2 sink is enabled\)]'
+    {-N,--no-playback}'[Disable video and audio playback]'
     '--no-key-repeat[Do not forward repeated key events when a key is held down]'
     '--no-mipmaps[Disable the generation of mipmaps]'
     '--no-power-on[Do not power on the device on start]'