Replace rtc::Optional with absl::optional

This is a no-op change because rtc::Optional is an alias to absl::optional

This CL generated by running script from modules with parameters
'pacing video_coding congestion_controller remote_bitrate_estimator':

find $@ -type f \( -name \*.h -o -name \*.cc \) \
-exec sed -i 's|rtc::Optional|absl::optional|g' {} \+ \
-exec sed -i 's|rtc::nullopt|absl::nullopt|g' {} \+ \
-exec sed -i 's|#include "api/optional.h"|#include "absl/types/optional.h"|' {} \+

find $@ -type f -name BUILD.gn \
-exec sed -r -i 's|"(../)*api:optional"|"//third_party/abseil-cpp/absl/types:optional"|' {} \+;

git cl format

Bug: webrtc:9078
Change-Id: I8ea501d7f1ee36e8d8cd3ed37e6b763c7fe29118
Reviewed-on: https://webrtc-review.googlesource.com/83900
Reviewed-by: Philip Eliasson <philipel@webrtc.org>
Commit-Queue: Danil Chapovalov <danilchap@webrtc.org>
Cr-Commit-Position: refs/heads/master@{#23640}
diff --git a/modules/congestion_controller/goog_cc/probe_controller.h b/modules/congestion_controller/goog_cc/probe_controller.h
index 163ccb2..c8946e8 100644
--- a/modules/congestion_controller/goog_cc/probe_controller.h
+++ b/modules/congestion_controller/goog_cc/probe_controller.h
@@ -16,7 +16,7 @@
 #include <initializer_list>
 #include <vector>
 
-#include "api/optional.h"
+#include "absl/types/optional.h"
 #include "api/transport/network_control.h"
 #include "rtc_base/constructormagic.h"
 
@@ -50,7 +50,7 @@
 
   void EnablePeriodicAlrProbing(bool enable);
 
-  void SetAlrStartTimeMs(rtc::Optional<int64_t> alr_start_time);
+  void SetAlrStartTimeMs(absl::optional<int64_t> alr_start_time);
   void SetAlrEndedTimeMs(int64_t alr_end_time);
 
   void RequestProbe(int64_t at_time_ms);
@@ -86,8 +86,8 @@
   int64_t start_bitrate_bps_;
   int64_t max_bitrate_bps_;
   int64_t last_bwe_drop_probing_time_ms_;
-  rtc::Optional<int64_t> alr_start_time_ms_;
-  rtc::Optional<int64_t> alr_end_time_ms_;
+  absl::optional<int64_t> alr_start_time_ms_;
+  absl::optional<int64_t> alr_end_time_ms_;
   bool enable_periodic_alr_probing_;
   int64_t time_of_last_large_drop_ms_;
   int64_t bitrate_before_last_large_drop_bps_;