Fix stripe issue in landcover level34

[emmaai]

As the title, changes:

• include only "clear" observation from wo for water_frequency and normalise against total valid observations.
• remove water_season from level1, use wo frequency band in level34 instead

The csv is updated accordingly https://dea-public-data-dev.s3-ap-southeast-2.amazonaws.com/lccs_validation/c3/data_to_plot/lccs_colour_scheme_golden_dark_au_c3.csv

[codecov]

Codecov Report

Attention: Patch coverage is 91.17647% with 3 lines in your changes missing coverage. Please review.

Project coverage is 81.20%. Comparing base (7e56476) to head (af02544).

Files with missing lines	Patch %	Lines
odc/stats/plugins/lc_fc_wo_a0.py	88.46%	3 Missing ⚠️

Additional details and impacted files

@@             Coverage Diff             @@
##           develop     #175      +/-   ##
===========================================
- Coverage    81.24%   81.20%   -0.04%     
===========================================
  Files           50       50              
  Lines         4532     4528       -4     
===========================================
- Hits          3682     3677       -5     
- Misses         850      851       +1     

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[tebadi]

I don't fully understand the logic but the code looks good.

[tebadi]

lear->clear