doc: fix some stale URLs

Author: matklad

src/doc/src/guide/dependencies.md

@@ -20,11 +20,11 @@ use. This example adds a dependency of the `time` crate:
 time = "0.1.12"
 ```
 
-The version string is a [semver] version requirement. The [specifying
+The version string is a [SemVer] version requirement. The [specifying
 dependencies](../reference/specifying-dependencies.md) docs have more information about
 the options you have here.
 
-[semver]: https://github.com/steveklabnik/semver#requirements
+[SemVer]: https://semver.org
 
 If we also wanted to add a dependency on the `regex` crate, we would not need
 to add `[dependencies]` for each crate listed. Here's what your whole

src/doc/src/reference/registries.md

@@ -222,9 +222,9 @@ explaining the format of the entry.
             // this is the new name. The original package name is stored in
             // the `package` field.
             "name": "rand",
-            // The semver requirement for this dependency.
+            // The SemVer requirement for this dependency.
             // This must be a valid version requirement defined at
-            // https://github.com/steveklabnik/semver#requirements.
+            // https://doc.rust-lang.org/cargo/reference/specifying-dependencies.html.
             "req": "^0.6",
             // Array of features (as strings) enabled for this dependency.
             "features": ["i128_support"],

src/doc/src/reference/specifying-dependencies.md

@@ -21,14 +21,16 @@ time = "0.1.12"
 
 The string `"0.1.12"` is a version requirement. Although it looks like a
 specific *version* of the `time` crate, it actually specifies a *range* of
-versions and allows SemVer compatible updates. An update is allowed if the new
+versions and allows [SemVer] compatible updates. An update is allowed if the new
 version number does not modify the left-most non-zero digit in the major, minor,
 patch grouping. In this case, if we ran `cargo update -p time`, cargo should
 update us to version `0.1.13` if it is the latest `0.1.z` release, but would not
 update us to `0.2.0`. If instead we had specified the version string as `1.0`,
 cargo should update to `1.1` if it is the latest `1.y` release, but not `2.0`.
 The version `0.0.x` is not considered compatible with any other version.
 
+[SemVer]: https://semver.org
+
 Here are some more examples of version requirements and the versions that would
 be allowed with them:
 
@@ -48,8 +50,8 @@ versions before 1.0.0. While SemVer says there is no compatibility before
 1.0.0, Cargo considers `0.x.y` to be compatible with `0.x.z`, where `y ≥ z`
 and `x > 0`.
 
-It is possible to further tweak the logic for selecting compatible version using
-special operators, though it shouldn't be necessary most of the time.
+It is possible to further tweak the logic for selecting compatible versions
+using special operators, though it shouldn't be necessary most of the time.
 
 ### Caret requirements