This PR converts relative imports to absolute imports in sklearn/utils/_fast_dict.pyx as part of the PyData Paris sprint (#32315).

Change made:

• Line 15: Changed from ._typedefs cimport float64_t, intp_t to from sklearn.utils._typedefs cimport float64_t, intp_t

Context:

• This is part of issue Use absolute imports in Cython code #32315, a coordinated effort to switch all Cython files to absolute imports
• I manually reviewed the file and identified the single relative import that needed conversion
• Following the pattern from the example PR MNT Switch to absolute imports in sklearn/cluster/_dbscan_inner.pyx #32316

Part of #32315