update the dependency pmezard/go-difflib

[neolit123]

What this PR does / why we need it:
A fmt.Sprintf() bug was fixed upstream.
Use the latest SHA from upstream.

Which issue(s) this PR fixes:

Fixes kubernetes/kubeadm#1368

Special notes for your reviewer:
followed the guide here:
https://github.com/kubernetes/community/blob/master/contributors/devel/sig-architecture/godep.md

but hack/run-in-gopath.sh hack/godep-save.sh fails for me with:

+++ [0212 01:54:31] Running godep save - this might take a while
godep: Package (github.com/bazelbuild/bazel-gazelle/cmd/gazelle) not found
!!! Error in hack/godep-save.sh:76
  Error in hack/godep-save.sh:76. 'GOPATH="${GOPATH}:$(pwd)/staging" ${KUBE_GODEP:?} save "${REQUIRED_BINS[@]}"' exited with status 1
Call stack:
  1: hack/godep-save.sh:76 main(...)
Exiting with status 1

so i sort of bootlegged the update.

Does this PR introduce a user-facing change?:

kubeadm: fix a bug in the underlying library for diff related to characters like '%'

/assign @dims @cblecker
/cc @chuckha
/area kubeadm
/kind bug
/priority important-soon

[neolit123]

/sig cluster-lifecycle

[cblecker]

Will review after tests pass.

[neolit123]

@cblecker relevant CI seems to have passed.

[chuckha]

Looks good to me. Thanks for figuring out how to do this!

[neolit123]

Looks good to me. Thanks for figuring out how to do this!

the existing process assumes a fast computer with fast internet.
next time i will write a small bash/sed script to update this in a equivalent way (for my local usage only).

[dims]

/lgtm

[dims]

@neolit123 right the existing docs is a hammer, but once you get the hang of it ... you can do a bunch of simple things by hand

[cblecker]

/lgtm
/approve

[k8s-ci-robot]

[APPROVALNOTIFIER] This PR is APPROVED

This pull-request has been approved by: cblecker, neolit123

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