Fix `is_homogeneous` weight bug #15024

Job	Run time
test-new	14m 33s
test-mod (sagemath_categories-check)	5m 34s
test-long (src/sage/[a-f]*)	37m 38s
test-long (src/sage/[g-o]*)	36m 1s
test-long (src/sage/[p-z]*)	39m 44s
test-long (src/doc src/sage_docbuild src/sage_setup)	13m 10s
coverage-report	18m 48s
	2h 45m 28s

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