gh-131987: Bump the magic number (#131991)

This should have been done as part of 053c285 but got blown away
in a merge.

Author: mpage

Diff for: Include/internal/pycore_magic_number.h

@@ -273,6 +273,7 @@ Known values:
     Python 3.14a6 3618 (Add oparg to END_ASYNC_FOR)
     Python 3.14a6 3619 (Renumber RESUME opcode from 149 to 128)
     Python 3.14a6 3620 (Optimize bytecode for all/any/tuple called on a genexp)
+    Python 3.14a7 3621 (Optimize LOAD_FAST opcodes into LOAD_FAST_BORROW)
 
     Python 3.15 will start with 3650
 
@@ -285,7 +286,7 @@ PC/launcher.c must also be updated.
 
 */
 
-#define PYC_MAGIC_NUMBER 3620
+#define PYC_MAGIC_NUMBER 3621
 /* This is equivalent to converting PYC_MAGIC_NUMBER to 2 bytes
    (little-endian) and then appending b'\r\n'. */
 #define PYC_MAGIC_NUMBER_TOKEN \