docs: update readme systemd files (#145)

### What does this PR do?

The centos bootc image now allows using `systemctl enable`

See: CentOS/centos-bootc#167

### Screenshot / video of UI

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screenshots or screencasts showing the difference -->

N/A

### What issues does this PR fix or reference?

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repository (or from another issue tracker). -->

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### How to test this PR?

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Signed-off-by: Charlie Drage <[email protected]>

docs/containerfile_guide.md

@@ -120,12 +120,8 @@ FROM quay.io/centos-bootc/fedora-bootc:eln
 # Add the systemd service
 ADD helloworld.service /usr/lib/systemd/system/helloworld.service
 
-# Equivilant "systemctl enable helloworld"
-# NOTE: Currently have to symlink until systemctl enable
-# functionality works in the future
-RUN ln -s \
-/usr/lib/systemd/system/helloworld.service \
-/usr/lib/systemd/system/default.target.wants/helloworld.service
+# Enable the service
+RUN systemctl enable helloworld
 
 # Add the helloworld example
 ADD helloworld.py /usr/bin/helloworld.py

examples/bootc-helloworld-python-systemd/Containerfile

@@ -3,11 +3,8 @@ FROM quay.io/centos-bootc/fedora-bootc:eln
 # Add the systemd service
 ADD helloworld.service /usr/lib/systemd/system/helloworld.service
 
-# Equivalent "systemctl enable helloworld"
-# will be implemented in the future
-RUN ln -s \
-/usr/lib/systemd/system/helloworld.service \
-/usr/lib/systemd/system/default.target.wants/helloworld.service
+# Enable the service
+RUN systemctl enable helloworld
 
 # Add the helloworld example
 ADD helloworld.py /usr/bin/helloworld.py