Drop linear-elasticity

It depends on Amiramesh which is dropped in dune-grid since 2.8

CHANGELOG.md

-# Master (will become release 2.8)
+# Master (will become release 2.9)
+
+## Deprecations and removals
+
+- The support of `Amiramesh` is dropped in dune-grid and thus the program `linear-elasticity` is removed from CMakeLists.txt
+
+# 2.8 Release
 
 - Introduce class `LocalDensity` for material-specific implementations
 - Introduce class `LocalIntegralEnergy` to work with the densities

src/CMakeLists.txt

 # Note: PYTHONLIBS_FOUND is only for backwards compatibility with dune-fufem 2.7 and can be removed
 #       in the next release
 if(ADOLC_FOUND AND IPOPT_FOUND AND ( Python3_FOUND OR PYTHONLIBS_FOUND )  AND dune-uggrid_FOUND)
-  set(programs linear-elasticity
-               finite-strain-elasticity)
+  set(programs finite-strain-elasticity)
+              #linear-elasticity depends on Amiramesh which is dropped since DUNE 2.8
 
   foreach(_program ${programs})
     add_executable(${_program} ${_program}.cc)