fix: update pretty-printer to work with gdb 17

Fixed an issue in `libcxx/utils/gdb/libcxx/printers.py`.

With gdb 17 (binutils 2_44) pretty-printers do not work anymore because calls to `gdb.printing` require `import gdb.printing` statement, which was missing from the printers.py

Broken after commit bminor/binutils-gdb@fc14343,
and `importgdb.printing` was first referenced in bminor/binutils-gdb@ee06c79

Author: kotborealis

libcxx/utils/gdb/libcxx/printers.py

@@ -14,6 +14,7 @@
 
 import re
 import gdb
+import gdb.printing
 
 # One under-documented feature of the gdb pretty-printer API
 # is that clients can call any other member of the API