Fix the issue where primal solver cannot be used in libmultilabel.

[zhi-bao]

What does this PR do?

Because the weight recalculation technique only applies to the L1/L2-SVM dual solver in LIBLINEAR, LIBLINEAR prohibits use of the other solvers when the w_recalc flag is set. However, LibMultiLabel always sets the w_recalc flag despite using the other solvers. To fix this issue, the w_recalc flag is now set only when using L1/L2-SVM dual solver.

Test CLI & API (bash tests/autotest.sh)

Test APIs used by main.py.

• Test Pass
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Check API Document

If any new APIs are added, please check if the description of the APIs is added to API document.

• API document is updated (linear, nn)
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Test quickstart & API (bash tests/docs/test_changed_document.sh)

If any APIs in quickstarts or tutorials are modified, please run this test to check if the current examples can run correctly after the modified APIs are released.

[Eleven1Liu]

@zhi-bao Please also bump the version to 0.7.3 (https://github.com/ntumlgroup/LibMultiLabel/blob/master/setup.cfg#L3) for release. Thanks.