TLS: only support TLS 1.2
TLS: only support TLS 1.2

TLS 1.0 and 1.1 are deprecated by major vendors (e.g. browsers).

Signed-off-by: Julien Pivotto <df1ed88a312a603dfee9f157a90fa8f7f195ab59@inuits.eu>

prometheus/exporter-toolkit