Fix build with OpenEXR 3

Add a header that is no longer transitively included
6 jobs for master in 13 minutes and 20 seconds
Status Job ID Name Coverage
  Prepare
passed #1281834
build-image

00:05:20

 
  Dependencies
passed #1281835
babl-master

00:02:59

failed #1281836
babl-min

00:02:51

 
  Gegl
passed #1281839
debug-fullconfig-master-babl

00:05:01

skipped #1281837
default-min-babl
passed #1281838
fullconfig-master-babl

00:04:10

 
Name Stage Failure
failed
babl-min Dependencies
Program tools/xml_insert.sh found: YES (/builds/GNOME/gegl/_babl/docs/tools/xml_insert.sh)
Configuring index-static.html using configuration
Program scp found: NO

docs/meson.build:147:0: ERROR: Program 'scp' not found

A full log can be found at /builds/GNOME/gegl/_babl/_build/meson-logs/meson-log.txt
Cleaning up file based variables
ERROR: Job failed: exit code 1