Fix: correct variables of 2020 and 2021 new data.

[KHwong12]

Summary

This branch corrects variables (column names and values) of 2020 and 2021 new data.

Changes

The changes made in this PR are:

1. Change the "SSPO" value in the district column of 2020 and 2021 data to "SSP". This keeps the district abbr in line with the original one.
2. Treat observations with easting and northing values of 800000 as NA values instead of valid spatial location. In raw data, 800000 refers to missing values.
3. Change the "collision_type" column variable in the pedestrian district dashboard to "collision_type_with_cycle". This replacement is missed in Feat: Add 2020 and 2021 collision data #113.

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Check

• (If UI & data are updated) The UI & data includes Traditional Chinese translation, with translation terms wrapped in i18n$t() and terms added to translation_zh.csv
• The GitHub Actions workflows pass.

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Note

Sequel for the leftover steps that should be completed in #113

[KHwong12]

Code used to correct and clean data available in https://gist.github.com/KHwong12/4e5d7e628ed8888cabe9cf511af323a7