Change default behaviour of SunZenithCorrector/sunz_corrected

[strandgren]

With #3397 it is suggested that the default behaviour of sunz_corrected modifier (SunZenithCorrector) should be changed to compute the true reflectance in Satpy >= 1.0. We would then have the sunz_corrected modifier that computes the true reflectance for scientific or quantitative use and the effective_solar_pathlength_corrected modifier which uses the Li and Shibata (2006) parameterization to avoid over-correction at high Sun zenith angels for (RGB) imagery.

For now, #3397 keeps the current default values and behavior (reduction of the sunz correction between 88-95 degrees), but with a warning that the default behavior will change in v1.0.

Hence, assuming that #3397 will be merged before Satpy v1.0, we need to do the following changes for Satpy v1.0:

• Change default values for correction_limit and max_sunz of SunZenithCorrector.
• Remove warning in SunZenithCorrector about changing defaults.
• Adapt expected output for testing default behaviour of SunZenithCorrector
• Remove deprecated class init input arguments and in EffectiveSolarPathLengthCorrector
• Remove warning in EffectiveSolarPathLengthCorrector about deprecated input arguments.
• Remove tests for warnings

For changing the default behaviour of SunZenithCorrector we basically need to revert this commit: f3b605d