BREAKING(dotenv): remove defaultsPath option from load[Sync]()

[iuioiua]

What's changed

The defaultsPath option has been removed from @std/dotenv/load.

Motivation

See details in #5464

Migration

To migrate, if you want to define default values for environment variables, do so in-code.

import "@std/dotenv/load";

+ if (!Deno.env.has("FOO")) {
+   Deno.env.set("FOO", "bar");
+ }

Related

Closes #5464

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 96.32%. Comparing base (2759686) to head (8e3e718).
Report is 1 commits behind head on main.

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #5451      +/-   ##
==========================================
- Coverage   96.33%   96.32%   -0.01%     
==========================================
  Files         463      463              
  Lines       37669    37651      -18     
  Branches     5555     5543      -12     
==========================================
- Hits        36289    36268      -21     
- Misses       1338     1341       +3     
  Partials       42       42              

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[kt3k]

Similarly to #5450, this handling of .env.default file seems opinionated, and it doesn't seem very common in the ecosystem.

I think it's reasonable to remove this feature from std/dotenv.

[PutziSan]

Noticed a small typo in the PR description: it states defaultPath was removed, but the actual name is defaultsPath. Just noting here in case anyone else searches for this change in the future.

[kt3k]

Thanks! Updated the PR title and description