fix(forge): do not warn on backward compatible solc_version config

[grandizzy]

Motivation

• solc_version is a backward compatible config (replaced by solc) and removed from dict, should not warn if in config
  

  foundry/crates/config/src/providers/ext.rs

  Lines 299 to 303 in 4d07808

  	} else if let Some(v) = dict.remove("solc_version") {
  	// only insert older variant if not already included
  	if !dict.contains_key("solc") {
  	dict.insert("solc".to_string(), v);
  	}

Solution

PR Checklist

• Added Tests
• Added Documentation
• Breaking changes