SpringBoot Update Github Actions configuration to correctly handle booleans that are actually strings

We have some places where, for example, inputs.java-toolchain is false. In this case the expressions ${{ inputs.java-toolchain && '8' || '' }} evaluates to 8 rather than the expected empty string. This happens because the input isn't treated as a boolean but as a string and any non-empty string is truthy. We need to use inputs.java-toolchain == 'true' instead.