doc: fix typo.

Doxyfile

@@ -266,7 +266,7 @@ ALIASES                = \
     "extension{2}=<a href=\"http://www.opengl.org/registry/specs/\1/\2.txt\"><tt>\1_\2</tt></a>" \
     "extension2{2}=<a href=\"http://www.opengl.org/registry/specs/\1/\1_\2.txt\"><tt>\1_\2</tt></a>" \
     "extension3{3}=<a href=\"http://www.opengl.org/registry/specs/\1/\3.txt\"><tt>\1_\2</tt></a>" \
-    "requires_gles20=@xrefitem requires-gles20 \"Requires OpenGL ES 2.0 / WebGL 1.%\" \"Functionality requiring OpenGL ES 2.0 or WebGL 1.0\"" \
+    "requires_gles20=@xrefitem requires-gles20 \"Requires OpenGL ES 2.0 / WebGL 1.0\" \"Functionality requiring OpenGL ES 2.0 or WebGL 1.0\"" \
     "requires_gles30=@xrefitem requires-gles30 \"Requires OpenGL ES 3.0\" \"Functionality requiring OpenGL ES 3.0\"" \
     "requires_gles31=@xrefitem requires-gles31 \"Requires OpenGL ES 3.1\" \"Functionality requiring OpenGL ES 3.1\"" \
     "requires_es_extension=@xrefitem requires-es-extension \"Requires OpenGL ES extension\" \"Functionality requiring specific OpenGL ES extension\"" \