Fix a stupid typo regarding SLEPc deactivation

CMakeLists.txt

@@ -192,7 +192,7 @@ if (PUGS_ENABLE_SLEPC MATCHES "^(AUTO|ON)$")
     pkg_check_modules(SLEPC SLEPc)
   else()
     message(STATUS "SLEPc support is deactivated since pugs will not be build with PETSc support")
-    set(SLEPc_FOUND FALSE)
+    set(SLEPC_FOUND FALSE)
     unset(PUGS_HAS_SLEPC)
   endif()
   set(PUGS_HAS_SLEPC ${SLEPC_FOUND})