[i2s_microphone] Partially revert #7092 so microphone volume doesn't change

[kahrendt]

What does this implement/fix?

PR #7092 modified how 32 bit microphone audio samples are converted to 16 bits. Previously, a 32 bit sample was bit shifted by 14 and then clamped to fit into an int16_t. This approach builds in a multiplication by a factor of 4. Most I2S microphone benefit for from this behavior. The PR changed it to bit shift by 16. While this new approach is the proper way to convert 32 bit audio samples to 16 bit, it has the unintended consequence of making a microphone samples quieter by a factor of 4 compared to before. This PR reverts to the old behavior of shifting by 14 bits and clamping so no other configuration changes are necessary to match the previous behavior.

We should eventually switch to shifting by 16 bits, but there needs to be a discussion on how to best handle that breaking change for existing configurations.

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): not applicable

Test Environment

• ESP32
• ESP32 IDF
• ESP8266
• RP2040
• BK72xx
• RTL87xx

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.

[codecov-commenter]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 53.78%. Comparing base (4d8b5ed) to head (ee9f9b6).
Report is 994 commits behind head on dev.

Additional details and impacted files

@@            Coverage Diff             @@
##              dev    #7109      +/-   ##
==========================================
+ Coverage   53.70%   53.78%   +0.07%     
==========================================
  Files          50       50              
  Lines        9408     9661     +253     
  Branches     1654     1705      +51     
==========================================
+ Hits         5053     5196     +143     
- Misses       4056     4141      +85     
- Partials      299      324      +25     

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[probot-esphome]

Hey there @jesserockz, mind taking a look at this pull request as it has been labeled with an integration (i2s_audio) you are listed as a code owner for? Thanks!
_{^{(message by CodeOwnersMention)}}