minor: Fix typo in nginx README

[arnd]

Fix a funny typo in Dry -> Try in Readme

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[k8s-reviewable]

This change is 

[coveralls]

Coverage decreased (-0.02%) to 45.982% when pulling f46aedd on arnd:master into aa02b7e on kubernetes:master.

[aledbf]

/lgtm

[k8s-ci-robot]

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In response to this comment:

/lgtm

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[aledbf]

@arnd please sign the cla

[arnd]

@aledbf I just signed it.

[aledbf]

@arnd thanks!