fix(bme280): fix bme280_read_altitude variable and unit bugs (AEGHB-1440)

[bkovacki]

Description

bme280_read_altitude had two bugs that made it always return incorrect results:

• Pressure was read into the unused temp variable instead of pressure, leaving pressure at 0.0
• pressure was then divided by 100 again despite bmp280_read_pressure already returning hPa, which would have produced an incorrect altitude even if the first bug were fixed

[github-actions]

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