Update linressims.def

Upgrading pip past 25.0 breaks build process

Author: JonahRileyHuggins

container/linressims.def

@@ -74,7 +74,6 @@ From: ubuntu:22.04
     ln -s /usr/bin/python3 /usr/bin/python
 
     # Set pip install locations to path
-    pip install --upgrade pip
     pip install dist/linressim-1.0-py3-none-any.whl --verbose --no-cache-dir
 
 %environment