Update RHEL8 dependencies in build instructions

Added perl-Time-Piece to the list of dependencies for RHEL8.

Author: magnesj

content/releases/build-from-source/build-instructions-ubuntu.md

@@ -35,7 +35,7 @@ Install GCC and related tools
 
 Dependencies for RHEL8
 
-    yum install curl zip unzip tar flex bison perl-IPC-Cmd gcc-toolset-10 freeglut
+    yum install curl zip unzip tar flex bison perl-IPC-Cmd gcc-toolset-10 freeglut perl-Time-Piece
 
 ### Clone and update sub modules
 
@@ -90,4 +90,4 @@ Set current working folder to the root folder of the ResInsight repository. Exec
     cd build
     ninja
 
-[CMake Configuration]({{% relref "cmake-configuration" %}})
+[CMake Configuration]({{% relref "cmake-configuration" %}})