[clang-tidy] Apply performance-inefficient-vector-operation fixes.

This CL applies clang-tidy's performance-inefficient-vector-operation
[1] on the WebRTC codebase.

All changes in this CL are automatically generated by both clang-tidy
and 'git cl format'.

[1] - https://clang.llvm.org/extra/clang-tidy/checks/performance-inefficient-vector-operation.html

Bug: webrtc:10252
Change-Id: I824caab2a5746036852e00d714b89aa5ec030ee3
Reviewed-on: https://webrtc-review.googlesource.com/c/120052
Commit-Queue: Mirko Bonadei <mbonadei@webrtc.org>
Reviewed-by: Karl Wiberg <kwiberg@webrtc.org>
Cr-Commit-Position: refs/heads/master@{#26442}

modules/audio_coding/codecs/builtin_audio_encoder_factory_unittest.cc

@@ -116,6 +116,7 @@ TEST(BuiltinAudioEncoderFactoryTest, SupportsTheExpectedFormats) {
 
   const std::vector<SdpAudioFormat> supported_formats = [&specs] {
     std::vector<SdpAudioFormat> formats;
+    formats.reserve(specs.size());
     for (const auto& spec : specs) {
       formats.push_back(spec.format);
     }