fix: skaffold diagnose outputs incorrect yaml for multiconfig projects

[gsquared94]

skaffold diagnose --yaml-only used on a multiconfig project outputs a merged list of all resolved configs.
For example:
skaffold.yaml:

...
requires:
  - path: ./skaffold2.yaml
build:
  - image: foo1
...

skaffold2.yaml:

...
build:
  - image: foo2
...

should produce:

...
build:
  - image: foo1
...
---
...
build:
  - image: foo2
...

But it's actually producing:

...
requires:
  - path: ./skaffold2.yaml
build:
  - image: foo1
...
---
...
build:
  - image: foo2
...

If this output yaml is used as the input for another skaffold run then the skaffold2.yaml artifacts are duplicated since it's reimported.
This PR fixes this issue by removing the dependency list prior to marshalling.

[codecov]

Codecov Report

Merging #5531 (bf42cab) into master (3160270) will increase coverage by 0.00%.
The diff coverage is 0.00%.

@@           Coverage Diff           @@
##           master    #5531   +/-   ##
=======================================
  Coverage   71.32%   71.33%           
=======================================
  Files         400      400           
  Lines       14831    14832    +1     
=======================================
+ Hits        10578    10580    +2     
  Misses       3475     3475           
+ Partials      778      777    -1     

Impacted Files	Coverage Δ
cmd/skaffold/app/cmd/diagnose.go	33.33% <0.00%> (-1.45%)	⬇️
pkg/skaffold/docker/parse.go	82.16% <0.00%> (-1.09%)	⬇️
pkg/skaffold/util/tar.go	56.00% <0.00%> (+5.33%)	⬆️

---

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[nkubala]

nice, thanks for jumping on this so quickly! tried it out and it works perfectly