[Cleanup] Remove write-only member _sndCardRecDelay.

The code was doing nothing except for triggering thread sanitizer,
since concurrent writes weren't guarded:
 * ReadRecordedData() through webrtc_audio_module_rec_thread
 * InitPlayout()      through main thread

Bug: webrtc:9751
Change-Id: I7ecf4fa436ff0695e5b998d7e3f159fb6c7e9214
Reviewed-on: https://webrtc-review.googlesource.com/c/src/+/146216
Reviewed-by: Henrik Andreassson <henrika@webrtc.org>
Commit-Queue: Yves Gerey <yvesg@google.com>
Cr-Commit-Position: refs/heads/master@{#28636}

modules/audio_device/linux/audio_device_pulse_linux.h

@@ -299,7 +299,6 @@ class AudioDeviceLinuxPulse : public AudioDeviceGeneric {
   bool quit_ RTC_GUARDED_BY(&_critSect);
 
   uint32_t _sndCardPlayDelay;
-  uint32_t _sndCardRecDelay;
 
   int32_t _writeErrors;