doc, man: ip-rule: Remove incorrect statement about rule 0

The documentation is wrong here: it is indeed possible to remove policy
rule 0 and recreate it afterwards. Therefore remove these statements.
Signed-off-by: Phil Sutter <phil@nwl.cc>

doc/ip-cref.tex

@@ -2049,9 +2049,6 @@ table \verb|local| (ID 255).
 The \verb|local| table is a special routing table containing
 high priority control routes for local and broadcast addresses.
 
-Rule 0 is special. It cannot be deleted or overridden.
-
-
 \item Priority: 32766, Selector: match anything, Action: lookup routing
 table \verb|main| (ID 254).
 The \verb|main| table is the normal routing table containing all non-policy

man/man8/ip-rule.8

@@ -118,8 +118,6 @@ The
 .B local
 table is a special routing table containing
 high priority control routes for local and broadcast addresses.
-.sp
-Rule 0 is special. It cannot be deleted or overridden.
 
 .TP
 2.