docs: Fix ubo indexing description

Ian points out that this being unrestricted was an oversight in the
spec, and is corrected in GLSL4.40.

Signed-off-by: Chris Forbes <chrisf@ijw.co.nz>
diff --git a/docs/GL3.txt b/docs/GL3.txt
index 686b141..0b663dd 100644
--- a/docs/GL3.txt
+++ b/docs/GL3.txt
@@ -103,7 +103,7 @@
   GL_ARB_gpu_shader5                                   started
   - 'precise' qualifier                                not started
   - Dynamically uniform sampler array indices          not started
-  - Unrestricted UBO array indices                     not started
+  - Dynamically uniform UBO array indices              not started
   - Implicit signed -> unsigned conversions            not started
   - Fused multiply-add                                 DONE
   - Packing/bitfield/conversion functions              DONE