registry: spec: Update XR_MNDX_egl_enable's version to 2

From 1.0.29, XR_MNDX_egl_enable changed the type of getProcAddress from
PFNEGLGETPROCADDRESSPROC to new added PFN_xrEglGetProcAddressMNDX. When
I tried to bump to this version for Monado, it caused compiling error
for Android NDK armeabi-v7a because new function type has extra
__attribute__ definition. From this experience, the 1.0.29's change
changed the extension APIs, and we might need to bump the version of
this extension to 2 to let Runtime and apps know it.

doc: Add documentation fragment

Signed-off-by: utzcoz <utzcoz@outlook.com>

changes/registry/pr.159.gh.OpenXR-Docs.md

@@ -0,0 +1 @@
+`XR_MNDX_egl_enable`: Update version to 2 to reflect function pointer type change.

changes/specification/pr.159.gh.OpenXR-Docs.md

@@ -0,0 +1 @@
+`XR_MNDX_egl_enable`: Update revision info and version to 2 to reflect function pointer type change.

specification/registry/xr.xml

@@ -7492,7 +7492,7 @@ maintained in the default branch of the Khronos OpenXR GitHub project.
 
     <extension name="XR_MNDX_egl_enable" number="49" type="instance" provisional="true" protect="XR_USE_PLATFORM_EGL" supported="openxr">
         <require>
-            <enum value="1"                              name="XR_MNDX_egl_enable_SPEC_VERSION"/>
+            <enum value="2"                              name="XR_MNDX_egl_enable_SPEC_VERSION"/>
             <enum value="&quot;XR_MNDX_egl_enable&quot;" name="XR_MNDX_EGL_ENABLE_EXTENSION_NAME"/>
             <enum offset="4" extends="XrStructureType"   name="XR_TYPE_GRAPHICS_BINDING_EGL_MNDX"/>
             <type name="XrGraphicsBindingEGLMNDX"/>

specification/sources/chapters/extensions/mndx/mndx_egl_enable.adoc

@@ -5,7 +5,7 @@
 include::{generated}/meta/XR_MNDX_egl_enable.adoc[]
 
 *Last Modified Date*::
-    2022-11-03
+    2023-12-02
 *IP Status*::
     No known IP claims.
 *Contributors*::
@@ -88,3 +88,8 @@ https://registry.khronos.org/EGL/sdk/docs/man/html/eglGetProcAddress.xhtml
 
 * Revision 1, 2020-05-20 (Jakob Bornecrantz)
 ** Initial draft
+
+* Revision 2, 2023-12-02
+** Use `PFN_xrEglGetProcAddressMNDX` to replace `PFNEGLGETPROCADDRESSPROC`
+   (for `eglGetProcAddress`).
+   Note this does change function pointer attributes on some platforms.