Switch to preshed v4

pyproject.toml

@@ -4,7 +4,7 @@ requires = [
     "cython>=0.25,<3.0",
     "murmurhash>=1.0.2,<1.1.0",
     "cymem>=2.0.2,<2.1.0",
-    "preshed>=3.0.2,<3.1.0",
+    "preshed>=4.0.0,<4.1.0",
     "blis>=0.7.8,<0.8.0",
     "numpy>=1.15.0",
 ]

requirements.txt

@@ -1,7 +1,7 @@
 # Explosion-provided dependencies
 murmurhash>=1.0.2,<1.1.0
 cymem>=2.0.2,<2.1.0
-preshed>=3.0.2,<3.1.0
+preshed>=4.0.0,<4.1.0
 blis>=0.7.8,<0.8.0
 srsly>=2.4.0,<3.0.0
 wasabi>=0.8.1,<1.2.0

setup.cfg

@@ -34,15 +34,15 @@ setup_requires =
     numpy>=1.15.0
     # We also need our Cython packages here to compile against 
     cymem>=2.0.2,<2.1.0
-    preshed>=3.0.2,<3.1.0
+    preshed>=4.0.0,<4.1.0
     murmurhash>=1.0.2,<1.1.0
     blis>=0.7.8,<0.8.0
 install_requires =
     # Explosion-provided dependencies
     blis>=0.7.8,<0.8.0
     murmurhash>=1.0.2,<1.1.0
     cymem>=2.0.2,<2.1.0
-    preshed>=3.0.2,<3.1.0
+    preshed>=4.0.0,<4.1.0
     wasabi>=0.8.1,<1.2.0
     srsly>=2.4.0,<3.0.0
     catalogue>=2.0.4,<2.1.0

thinc/backends/numpy_ops.pyx

@@ -12,7 +12,6 @@ from libc.stdint cimport uint32_t, uint64_t
 from libc.string cimport memcpy
 from libc.math cimport isnan
 from cymem.cymem cimport Pool
-from preshed.maps cimport PreshMap
 from murmurhash.mrmr cimport hash64
 cimport numpy as np