Do not use deprecated func NewConfigFromConfigMap in deprecated_config.go

[nak3]

Although NewConfigFromConfigMap is not marked, it is a function in deprecated_config.go.
knative/networking#787 is making as deprecated.

This patch changes to use a func in knative.dev/networking/pkg/config, instead.

/cc @dprotaso

[knative-prow]

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[nak3]

xref: knative/networking#787

[codecov]

Codecov Report

Patch coverage has no change and project coverage change: -0.09 ⚠️

Comparison is base (dab78d1) 86.33% compared to head (612ff9b) 86.25%.

Additional details and impacted files

@@            Coverage Diff             @@
##             main   #13847      +/-   ##
==========================================
- Coverage   86.33%   86.25%   -0.09%     
==========================================
  Files         198      198              
  Lines       14669    14669              
==========================================
- Hits        12665    12653      -12     
- Misses       1708     1716       +8     
- Partials      296      300       +4     

Impacted Files	Coverage Δ
cmd/activator/main.go	0.00% <0.00%> (ø)

... and 3 files with indirect coverage changes

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[nak3]

/hold

There are other places where use the NewConfigFromConfigMap(). Probably it is better to add NewConfigFromConfigMap in networking/pkg/config.

[nak3]

Closing as per knative/networking#787 (comment)