python: Avoid warning about using deprecated methods

Fixes gstreamer/gst-editing-services#69
12 jobs for python_deprecated_warning in 34 minutes and 41 seconds (queued for 2 seconds)
Status Job ID Name Coverage
  Preparation
passed #281903
gst indent

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passed #281902
manifest

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  Build
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build fedora x86_64

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build nodebug fedora x86_64

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  Test
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check fedora

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integration testsuites fedora

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  Full Builds
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build cerbero android universal

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build cerbero cross win32

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passed #281911
build cerbero cross win64

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build cerbero fedora x86_64

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  Full Tests
passed #281912
valgrind ges

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  Apps
passed #281913
android universal examples

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