Add minimum version of Thrift in Jaeger exporter build instructions

[varunsh-xilinx]

Describe your environment

Ubuntu 16.04 with Apache Thrift 0.12.0 and trying to build opentelemetry-cpp v1.1.0

Steps to reproduce

cmake -DWITH_JAEGER=ON -DBUILD_TESTING=OFF -DWITH_EXAMPLES=OFF -DWITH_PROMETHEUS=ON ..
make -j

What is the expected behavior?
Building should succeed or should make clear why it doesn't work

What is the actual behavior?
The build fails with this error:

opentelemetry-cpp-1.1.0/exporters/jaeger/src/THttpTransport.h:23:8: error: ‘bool opentelemetry::v1::exporter::jaeger::THttpTransport::isOpen() const’ marked ‘override’, but does not override
   23 |   bool isOpen() const override;

Additional context
So the reason this fails is that Apache Thrift 0.12.0 doesn't mark isOpen() as const so the override fails. Thrift 0.13.0 does mark it const but there may be other build issues with this version. I was able to build with 0.15.0 at least. Could you add some information about what versions of Thrift work in the documentation? Or assert the version in the CMake build?

[lalitb]

The versions used in CI env are populated here: https://github.com/open-telemetry/opentelemetry-cpp/blob/main/third_party_release. So it's 0.14.1 for thrift.
But agree, it can be documented more explicitly. Will remove the bug label, and add doc.