Update docs to bump libjemalloc version on latest debian; correct "push_rules" stream name

changelog.d/17171.doc

@@ -0,0 +1,2 @@
+Update the Admin FAQ with the current libjemalloc version for latest Debian stable.
+Update name of the "push_rules" stream in docs/workers.md

docs/usage/administration/admin_faq.md

@@ -250,10 +250,10 @@ Using [libjemalloc](https://jemalloc.net) can also yield a significant
 improvement in overall memory use, and especially in terms of giving back
 RAM to the OS. To use it, the library must simply be put in the
 LD_PRELOAD environment variable when launching Synapse. On Debian, this
-can be done by installing the `libjemalloc1` package and adding this
+can be done by installing the `libjemalloc2` package and adding this
 line to `/etc/default/matrix-synapse`:
 
-    LD_PRELOAD=/usr/lib/x86_64-linux-gnu/libjemalloc.so.1
+    LD_PRELOAD=/usr/lib/x86_64-linux-gnu/libjemalloc.so.2
 
 This made a significant difference on Python 2.7 - it's unclear how
 much of an improvement it provides on Python 3.x.

docs/workers.md

@@ -535,7 +535,7 @@ the stream writer for the `presence` stream:
 ##### The `push_rules` stream
 
 The following endpoints should be routed directly to the worker configured as
-the stream writer for the `push` stream:
+the stream writer for the `push_rules` stream:
 
     ^/_matrix/client/(api/v1|r0|v3|unstable)/pushrules/