[Profiling, 9.0.0] Remove backwards compatibility code in CO2 calculator

[rockdaboot]

elasticsearch/x-pack/plugin/profiling/src/main/java/org/elasticsearch/xpack/profiling/CO2Calculator.java

Line 57 in 8a7697b

// For the OTEL donation of the profiling agent, we switch to OTEL semantic conventions,

[elasticsearchmachine]

Pinging @elastic/obs-knowledge-team (Team:obs-knowledge)