[Reverb] Fix the build.

TF moved to C++17, where absl::string_view is std::string_view; which led
to a bunch of linker errors since we're still building with C++14 mode.

I was able to debug this *only* because I saw Mihai's tweet last week:
  https://twitter.com/mihaimaruseac/status/1528548118576365571

... which makes me inexplicably angry :<E (not at Mihai).
We shouldn't be finding out about breaking changes via twitter.

PiperOrigin-RevId: 452581699
Change-Id: I52024fac3ca44a743dc73de578e0b6ad799a55fe

.bazelrc

@@ -12,7 +12,7 @@ build --python_path=python3
 build:manylinux2014 --crosstool_top=//third_party/toolchains/preconfig/ubuntu16.04/gcc7_manylinux2014:toolchain
 
 build -c opt
-build --cxxopt="-std=c++14"
+build --cxxopt="-std=c++17"
 # We can emove this flag (we keep it explicit for now)
 build --cxxopt="-D_GLIBCXX_USE_CXX11_ABI=1"
 build --auto_output_filter=subpackages