migration-guides: system-conf -> systemd-conf

Fix this typo. There is no system-conf recipe.

(From yocto-docs rev: 6c1ef81cce2e211ad2fd2cf5f98ce0cfebbf56f7)

Signed-off-by: Etienne Cordonnier <ecordonnier@snap.com>
Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>

documentation/migration-guides/migration-2.6.rst

@@ -277,13 +277,13 @@ The following changes have occurred:
    See the ":ref:`bitbake-user-manual/bitbake-user-manual-metadata:removal (override style syntax)`"
    section in the BitBake User Manual for a detailed example.
 
-.. _migration-2.6-systemd-configuration-now-split-out-to-system-conf:
+.. _migration-2.6-systemd-configuration-now-split-out-to-systemd-conf:
 
 ``systemd`` Configuration is Now Split Into ``systemd-conf``
 ------------------------------------------------------------
 
 The configuration for the ``systemd`` recipe has been moved into a
-``system-conf`` recipe. Moving this configuration to a separate recipe
+``systemd-conf`` recipe. Moving this configuration to a separate recipe
 avoids the ``systemd`` recipe from becoming machine-specific for cases
 where machine-specific configurations need to be applied (e.g. for
 ``qemu*`` machines).