fix typo Linael -> Linear

[TobiKattmann]

Proposed Changes

Description of LINEAR_SOLVER_ILU_FILL_IN wrote Linael instead of Linear .. and that was copied quite a few times
Done using find ./ -type -f -exec sed -i -e 's/Linael/Linear/g' {} \; in ./Testcases on Linux

As in none of the appearances the option is not using the default of zero, that option could be removed from all those testcases imo, but I put that up to discussion. As @pcarruscag mentioned in #1195 [...]simplify the config by removing options that are not needed, this is to make it easier to maintain the testcases if there are changes to some options.

Feel free to chip any other typos here.

Related Work

Seen in #1195 and annoyed me enough to open a PR, but of course not introduced there

• I am submitting my contribution to the develop branch.
• My contribution generates no new compiler warnings (try with the '-Wall -Wextra -Wno-unused-parameter -Wno-empty-body' compiler flags, or simply --warnlevel=2 when using meson).
• My contribution is commented and consistent with SU2 style.
• I have added a test case that demonstrates my contribution, if necessary.
• I have updated appropriate documentation (Tutorials, Docs Page, config_template.cpp) , if necessary.

[pcarruscag]

Oh no... even the template xD