Correctly document default value of fork-strategy setting (#9931)

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## Summary

The `fork-strategy` default value was overlooked in #9887.

---------

Co-authored-by: Charlie Marsh <charlie.r.marsh@gmail.com>

crates/uv-settings/src/settings.rs

@@ -497,7 +497,7 @@ pub struct ResolverInstallerOptions {
     /// preferring older versions that are compatible with a wider range of supported Python
     /// versions or platforms.
     #[option(
-        default = "\"fewest\"",
+        default = "\"requires-python\"",
         value_type = "str",
         example = r#"
             fork-strategy = "fewest"
@@ -1099,7 +1099,7 @@ pub struct PipOptions {
     /// preferring older versions that are compatible with a wider range of supported Python
     /// versions or platforms.
     #[option(
-        default = "\"fewest\"",
+        default = "\"requires-python\"",
         value_type = "str",
         example = r#"
             fork-strategy = "fewest"

docs/reference/settings.md

@@ -777,7 +777,7 @@ Under `fewest`, uv will minimize the number of selected versions for each packag
 preferring older versions that are compatible with a wider range of supported Python
 versions or platforms.
 
-**Default value**: `"fewest"`
+**Default value**: `"requires-python"`
 
 **Possible values**:
 
@@ -2158,7 +2158,7 @@ Under `fewest`, uv will minimize the number of selected versions for each packag
 preferring older versions that are compatible with a wider range of supported Python
 versions or platforms.
 
-**Default value**: `"fewest"`
+**Default value**: `"requires-python"`
 
 **Possible values**: