Issue #29109: Enhance tracemalloc documentation

* Wrong parameter name, 'group_by' instead of 'key_type'
* Don't round up numbers when explaining the examples. If they exactly match
  what can be read in the script output, it is to easier to understand
  (4.8 MiB vs 4855 KiB)
* Fix incorrect method link that was pointing to another module

Patch written by Loic Pefferkorn.
diff --git a/Misc/ACKS b/Misc/ACKS
index 35b2611..06c7a93 100644
--- a/Misc/ACKS
+++ b/Misc/ACKS
@@ -1127,6 +1127,7 @@
 Randy Pausch
 Samuele Pedroni
 Justin Peel
+Loic Pefferkorn
 Marcel van der Peijl
 Berker Peksag
 Andreas Pelme