[CI/Build] Drop Python 3.8 support (#10038)

Signed-off-by: Russell Bryant <rbryant@redhat.com>
Signed-off-by: DarkLight1337 <tlleungac@connect.ust.hk>
Co-authored-by: DarkLight1337 <tlleungac@connect.ust.hk>

setup.py

@@ -55,12 +55,6 @@ def is_ninja_available() -> bool:
     return which("ninja") is not None
 
 
-def remove_prefix(text, prefix):
-    if text.startswith(prefix):
-        return text[len(prefix):]
-    return text
-
-
 class CMakeExtension(Extension):
 
     def __init__(self, name: str, cmake_lists_dir: str = '.', **kwa) -> None:
@@ -197,8 +191,10 @@ class cmake_build_ext(build_ext):
             os.makedirs(self.build_temp)
 
         targets = []
-        target_name = lambda s: remove_prefix(remove_prefix(s, "vllm."),
-                                              "vllm_flash_attn.")
+
+        def target_name(s: str) -> str:
+            return s.removeprefix("vllm.").removeprefix("vllm_flash_attn.")
+
         # Build all the extensions
         for ext in self.extensions:
             self.configure(ext)