[rand.req] Fix table headers for longtable continued on following page

Fixes ISO/CS comment (C++23 proof)

Author: jensmaurer

source/numerics.tex

@@ -1920,7 +1920,8 @@
   & \rhdr{Complexity}
   \\ \capsep
 \endfirsthead
-\hline
+\continuedcaption\\
+\topline
 \lhdr{Expression}
   & \chdr{Return type}
   & \chdr{Pre/post-condition}
@@ -2308,7 +2309,8 @@
   & \rhdr{Complexity}
   \\ \capsep
 \endfirsthead
-\hline
+\continuedcaption\\
+\topline
 \lhdr{Expression}
   & \chdr{Return type}
   & \chdr{Pre/post-condition}