Upgrade libdparse (remove deprecation warnings)

[wilzbach]

In the spirit of removing deprecation warnings, s.t. they don't bite us later.

../../../.dub/packages/libdparse-0.7.0/libdparse/src/dparse/ast.d(1346,10): Deprecation: cannot implicitly override base class method object.Object.opEquals with dparse.ast.Declaration.opEquals; add override attribute
tests_extractor ~master: building configuration "application"...
../../../.dub/packages/libdparse-0.7.0/libdparse/src/dparse/ast.d(1346,10): Deprecation: cannot implicitly override base class method object.Object.opEquals with dparse.ast.Declaration.opEquals; add override attribute

[dlang-bot]

Thanks for your pull request, @wilzbach!

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