Remove the "Up to 2" buffered frames option

Three frames in flight showed no performance benefit over two, so drop
the option and clamp existing configs (and the default) down to 2.
The now-unused "Up to 2" translation keys are left in place.

Fixes #21419

Co-Authored-By: Claude Opus 5 (1M context) <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01JvJR8oJNSCimCM9KXVLjfq

Core/Config.cpp

@@ -755,7 +755,7 @@ static const ConfigSetting graphicsSettings[] = {
 	ConfigSetting("GfxDebugOutput", SETTING(g_Config, bGfxDebugOutput), false, CfgFlag::DONT_SAVE),
 	ConfigSetting("LogFrameDrops", SETTING(g_Config, bLogFrameDrops), false, CfgFlag::DEFAULT),
 
-	ConfigSetting("InflightFrames", SETTING(g_Config, iInflightFrames), 3, CfgFlag::DEFAULT),
+	ConfigSetting("InflightFrames", SETTING(g_Config, iInflightFrames), 2, CfgFlag::DEFAULT),
 	ConfigSetting("RenderDuplicateFrames", SETTING(g_Config, bRenderDuplicateFrames), false, CfgFlag::PER_GAME),
 
 	ConfigSetting("MultiThreading", SETTING(g_Config, bRenderMultiThreading), true, CfgFlag::DEFAULT),
@@ -1611,6 +1611,9 @@ void Config::PostLoadCleanup() {
 
 	// Clamp save state slot count to somewhat sane limits.
 	iSaveStateSlotCount = std::clamp(iSaveStateSlotCount, 1, 100);
+
+	// Three frames in flight showed no benefit over two, so the option is gone. Squash old values.
+	iInflightFrames = std::clamp(iInflightFrames, 1, 2);
 }
 
 void Config::PreSaveCleanup() {

libretro/libretro.cpp

@@ -778,8 +778,6 @@ static void check_variables(CoreParameter &coreParam)
          g_Config.iInflightFrames = 1;
       else if (!strcmp(var.value, "Up to 1"))
          g_Config.iInflightFrames = 2;
-      else if (!strcmp(var.value, "Up to 2"))
-         g_Config.iInflightFrames = 3;
    }
 
    var.key = "ppsspp_skip_buffer_effects";

libretro/libretro_core_options.h

@@ -436,10 +436,9 @@ struct retro_core_option_v2_definition option_defs_us[] = {
       {
          { "No buffer", NULL },
          { "Up to 1",   NULL },
-         { "Up to 2",   NULL },
          { NULL, NULL },
       },
-      "Up to 2"
+      "Up to 1"
    },
    {
       "ppsspp_button_preference",