Replace rtc::Optional with absl::optional in audio, call and video

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

This CL generated by running script with parameters 'audio call video':
#!/bin/bash
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: I02c5db956846a88a268a300ba086703a02d62e36
Reviewed-on: https://webrtc-review.googlesource.com/83722
Reviewed-by: Karl Wiberg <kwiberg@webrtc.org>
Commit-Queue: Danil Chapovalov <danilchap@webrtc.org>
Cr-Commit-Position: refs/heads/master@{#23628}
diff --git a/call/rtp_bitrate_configurator_unittest.cc b/call/rtp_bitrate_configurator_unittest.cc
index d5eed23..b177db7 100644
--- a/call/rtp_bitrate_configurator_unittest.cc
+++ b/call/rtp_bitrate_configurator_unittest.cc
@@ -13,7 +13,7 @@
 #include "test/gtest.h"
 
 namespace webrtc {
-using rtc::nullopt;
+using absl::nullopt;
 
 class RtpBitrateConfiguratorTest : public testing::Test {
  public:
@@ -21,10 +21,10 @@
       : configurator_(new RtpBitrateConfigurator(BitrateConstraints())) {}
   std::unique_ptr<RtpBitrateConfigurator> configurator_;
   void UpdateConfigMatches(BitrateConstraints bitrate_config,
-                           rtc::Optional<int> min_bitrate_bps,
-                           rtc::Optional<int> start_bitrate_bps,
-                           rtc::Optional<int> max_bitrate_bps) {
-    rtc::Optional<BitrateConstraints> result =
+                           absl::optional<int> min_bitrate_bps,
+                           absl::optional<int> start_bitrate_bps,
+                           absl::optional<int> max_bitrate_bps) {
+    absl::optional<BitrateConstraints> result =
         configurator_->UpdateWithSdpParameters(bitrate_config);
     EXPECT_TRUE(result.has_value());
     if (start_bitrate_bps.has_value())
@@ -36,10 +36,10 @@
   }
 
   void UpdateMaskMatches(BitrateSettings bitrate_mask,
-                         rtc::Optional<int> min_bitrate_bps,
-                         rtc::Optional<int> start_bitrate_bps,
-                         rtc::Optional<int> max_bitrate_bps) {
-    rtc::Optional<BitrateConstraints> result =
+                         absl::optional<int> min_bitrate_bps,
+                         absl::optional<int> start_bitrate_bps,
+                         absl::optional<int> max_bitrate_bps) {
+    absl::optional<BitrateConstraints> result =
         configurator_->UpdateWithClientPreferences(bitrate_mask);
     EXPECT_TRUE(result.has_value());
     if (start_bitrate_bps.has_value())