Fix istio getting started guide

[dharaneeshvrd]

What type of PR is this?

What this PR does / why we need it:
Fix istio getting started guide by reordering the steps since inference pool helm chart requires istio CRDs to be present before installing the chart due to recent change #1381.

Which issue(s) this PR fixes:

Fixes #1649

Does this PR introduce a user-facing change?:

NONE

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[dharaneeshvrd]

/cc @nirrozenbaum
could you please review this fix?

[kfswain]

Hi @dharaneeshvrd thanks for the PR. Are we certain this is broken? Looking at the docs it seems like everything is WAI and all other GW implementations have the install step lower down in the guide.

[dharaneeshvrd]

@kfswain Yes currently all GW implementations are having the install step lower down the guide but it seems due to #1381 this recent change, inferencepool helm chart for istio provider requires istio's DestinationRule CRD to be present first. Hence for istio alone moved the installation step before installing the inferencepool helm chart like its being requested in the issue #1649.