Fix typo in documentation

[kapily]

What does this implement/fix?

Fix typos in documentation.
See this related PR:
esphome/esphome-docs#3207

The documentation says specifically the PMC (particulate matter counts) refer to counts of particles greater than a given size.

https://esphome.io/components/sensor/pmsa003i.html:
"Count of particles with diameter > 1 um in 0.1 L of air"
But the code documentation is wrong

Types of changes

• Bugfix (non-breaking change which fixes an issue)
• New feature (non-breaking change which adds functionality)
• Breaking change (fix or feature that would cause existing functionality to not work as expected)
• Other

Related issue or feature (if applicable): fixes

Pull request in esphome-docs with documentation (if applicable): esphome/esphome-docs#

Test Environment

• ESP32
• ESP32 IDF
• ESP8266
• RP2040

Example entry for config.yaml:

# Example config.yaml

Checklist:

• The code change is tested and works locally.
• Tests have been added to verify that the new code works (under tests/ folder).

If user exposed functionality or configuration variables are added/changed:

• Documentation added/updated in esphome-docs.

[probot-esphome]

Hey there @sjtrny, mind taking a look at this pull request as it has been labeled with an integration (pmsa003i) you are listed as a code owner for? Thanks!
_{^{(message by CodeOwnersMention)}}