Is this command required to enable saml in Liberty server?
bin/installUtility install samlWeb-2.0
I have configured <feature>samlWeb-2.0</feature> in my server.xml and able to get metadata file using the url https://ip:port/ibm/saml20/defaultSP/samlmetadata
It's <feature>samlWeb-2.0</feature> that enables the feature, but you can't enable what you don't have, which is where bin/installUtility would come in (if necessary).
Liberty is available in several packages which dictate which set/sub-set of features are available immediately after installation (custom packages of Liberty can also be created to further customize the available set of features available to the runtime). Features that are not included in the package can be installed afterwards using bin/installUtility (bin/featureManager has been deprecated).
The command bin/installUtility install samlWeb-2.0 retrieves (from a repo) and installs the samlWeb-2.0 feature if it wasn't already installed in your Liberty runtime. For example, if the Liberty package was that of just the Liberty Kernel, than bin/installUtility install samlWeb-2.0 would download the samlWeb-2.0 feature along with all other pre-req features. However, if your Liberty package was that of the entire Base edition (wlp-base-all) than it would already include the samlWeb-2.0 feature and you would not need to run bin/installUtility prior to enabling it.