chore: force pip version greater than v26

We need it for Python 3.15 support.
Otherwise, TypeError: Can't instantiate abstract class WheelDistribution without an implementation for abstract method 'locate_file'

Author: Xmader

poetry.lock

@@ -63,7 +63,11 @@ pmjs = "pythonmonkey.cli.pmjs:main"
 
 [tool.poetry.group.dev.dependencies]
 pytest = "^7.3.1"
-pip = "^23.1.2"
+pip = [
+  {version = "^26.2.1", python = ">=3.10"},      # Needed for Python 3.15 support,
+                                                 # otherwise TypeError: Can't instantiate abstract class WheelDistribution...
+  {version = "^23.1.2", python = ">=3.8,<3.10"},
+]
 numpy = [
   {version = "^2.5.0", python = ">=3.12"},
   {version = "^2.3.0", python = ">=3.11,<3.12"}, # NumPy 2.5.0  drops support for Python 3.11