[AKS] Fix --aks-mcp flag to accept true/false values (#9231)

Simplified the aks-mcp parameter by removing custom positive/negative labels
and using the default three_state_flag behavior to properly handle true/false values.

Author: feiskyer

src/aks-agent/HISTORY.rst

@@ -11,6 +11,7 @@ To release a new version, please select a new version number (usually plus 1 to
 
 Pending
 +++++++
+* Fix the --aks-mcp flag to allow true/false values.
 
 1.0.0b3
 +++++++

src/aks-agent/azext_aks_agent/_params.py

@@ -90,10 +90,7 @@ def load_arguments(self, _):
             "use_aks_mcp",
             options_list=["--aks-mcp"],
             default=False,
-            arg_type=get_three_state_flag(
-                positive_label="Enable AKS MCP integration",
-                negative_label="Disable AKS MCP integration",
-            ),
+            arg_type=get_three_state_flag(),
             help=(
                 "Enable AKS MCP integration for enhanced capabilities. "
                 "Traditional mode is the default. Use --aks-mcp to enable MCP mode, or "