SDL: Sync SDL3 wiki -> header (bdde0)

From bdde074688cd63c18eb204652765613adf2c1269 Mon Sep 17 00:00:00 2001
From: SDL Wiki Bot <[EMAIL REDACTED]>
Date: Wed, 5 Mar 2025 22:49:13 +0000
Subject: [PATCH] Sync SDL3 wiki -> header

[ci skip]
---
 include/SDL3/SDL_gamepad.h | 6 ++++--
 1 file changed, 4 insertions(+), 2 deletions(-)

diff --git a/include/SDL3/SDL_gamepad.h b/include/SDL3/SDL_gamepad.h
index 99f8b6593fab6..07a39b55233d8 100644
--- a/include/SDL3/SDL_gamepad.h
+++ b/include/SDL3/SDL_gamepad.h
@@ -1156,10 +1156,12 @@ extern SDL_DECLSPEC bool SDLCALL SDL_GamepadHasAxis(SDL_Gamepad *gamepad, SDL_Ga
  * return a negative value. Note that this differs from the value reported by
  * the lower-level SDL_GetJoystickAxis(), which normally uses the full range.
  *
+ * Note that for invalid gamepads or axes, this will return 0. Zero is also a
+ * valid value in normal operation; usually it means a centered axis.
+ *
  * \param gamepad a gamepad.
  * \param axis an axis index (one of the SDL_GamepadAxis values).
- * \returns axis state (including 0) on success or 0 (also) on failure; call
- *          SDL_GetError() for more information.
+ * \returns axis state.
  *
  * \since This function is available since SDL 3.2.0.
  *