Upgrade pip from 25.2 -> 25.3 (#826)

Author: mmangkad

pythonbuild/downloads.py

@@ -293,10 +293,10 @@
         "version": "0.13.1",
     },
     "pip": {
-        "url": "https://files.pythonhosted.org/packages/b7/3f/945ef7ab14dc4f9d7f40288d2df998d1837ee0888ec3659c813487572faa/pip-25.2-py3-none-any.whl",
-        "size": 1752557,
-        "sha256": "6d67a2b4e7f14d8b31b8b52648866fa717f45a1eb70e83002f4331d07e953717",
-        "version": "25.2",
+        "url": "https://files.pythonhosted.org/packages/44/3c/d717024885424591d5376220b5e836c2d5293ce2011523c9de23ff7bf068/pip-25.3-py3-none-any.whl",
+        "size": 1778622,
+        "sha256": "9655943313a94722b7774661c21049070f6bbb0a1516bf02f7c8d5d9201514cd",
+        "version": "25.3",
     },
     "readline": {
         # Mirrored from https://ftp.gnu.org/gnu/readline/readline-8.2.tar.gz