[Rule Tuning] Add Supplemental Mitre Mappings (#5876)

---------

Co-authored-by: Ruben Groenewoud <78494512+Aegrah@users.noreply.github.com>
Co-authored-by: Isai <59296946+imays11@users.noreply.github.com>
Co-authored-by: terrancedejesus <terrance.dejesus@elastic.co>
Co-authored-by: Jonhnathan <26856693+w0rk3r@users.noreply.github.com>
Co-authored-by: eric-forte-elastic <eric.forte@elastic.co>

rules/linux/command_and_control_potential_tunneling_command_line.toml

@@ -2,7 +2,7 @@
 creation_date = "2025/12/12"
 integration = ["endpoint", "crowdstrike", "sentinel_one_cloud_funnel", "auditd_manager"]
 maturity = "production"
-updated_date = "2025/12/12"
+updated_date = "2026/03/24"
 
 [transform]
 [[transform.osquery]]
@@ -170,6 +170,11 @@ process.command_line regex """.*[0-9]{1,3}\.[0-9]{1,3}\.[0-9]{1,3}\.[0-9]{1,3}:[
 [[rule.threat]]
 framework = "MITRE ATT&CK"
 
+[[rule.threat.technique]]
+id = "T1090"
+name = "Proxy"
+reference = "https://attack.mitre.org/techniques/T1090/"
+
 [[rule.threat.technique]]
 id = "T1572"
 name = "Protocol Tunneling"