SEADAS: MERIS Logical Expression Fix

[knowles]

Fixes error in MERIS logical expression. Note elsewhere this expression is already fixed in the file opttbx-sentinel3-reader/src/main/java/eu/esa/opt/dataio/s3/meris/MerisLevel1ProductPlugIn.java

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[TomBlock]

Good morning Danny, good finding, thank you. I have refactored this code a bit, please check if this PR is ok for you.

#71