Fix the description of the "root" field of the cargo metadata's output (#15182)

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Fixes #15181.

Author: weihanglo

src/doc/man/cargo-metadata.md

@@ -312,9 +312,9 @@ The JSON output has the following format:
                 ]
             }
         ],
-        /* The root package of the workspace.
-           This is null if this is a virtual workspace. Otherwise it is
-           the Package ID of the root package.
+        /* The package in the current working directory (if --manifest-path is not given).
+           This is null if there is a virtual workspace. Otherwise it is
+           the Package ID of the package.
         */
         "root": "file:///path/to/my-package#0.1.0",
     },
@@ -359,7 +359,7 @@ possible value.
 
 {{#option "`--filter-platform` _triple_" }}
 This filters the `resolve` output to only include dependencies for the
-given [target triple](../appendix/glossary.html#target). 
+given [target triple](../appendix/glossary.html#target).
 Without this flag, the resolve includes all targets.
 
 Note that the dependencies listed in the "packages" array still includes all

src/doc/man/generated_txt/cargo-metadata.txt

@@ -308,9 +308,9 @@ OUTPUT FORMAT
                            ]
                        }
                    ],
-                   /* The root package of the workspace.
-                      This is null if this is a virtual workspace. Otherwise it is
-                      the Package ID of the root package.
+                   /* The package in the current working directory (if --manifest-path is not given).
+                      This is null if there is a virtual workspace. Otherwise it is
+                      the Package ID of the package.
                    */
                    "root": "file:///path/to/my-package#0.1.0",
                },

src/doc/src/commands/cargo-metadata.md

@@ -312,9 +312,9 @@ The JSON output has the following format:
                 ]
             }
         ],
-        /* The root package of the workspace.
-           This is null if this is a virtual workspace. Otherwise it is
-           the Package ID of the root package.
+        /* The package in the current working directory (if --manifest-path is not given).
+           This is null if there is a virtual workspace. Otherwise it is
+           the Package ID of the package.
         */
         "root": "file:///path/to/my-package#0.1.0",
     },

src/etc/man/cargo-metadata.1

@@ -314,9 +314,9 @@ The JSON output has the following format:
                 ]
             }
         ],
-        /* The root package of the workspace.
-           This is null if this is a virtual workspace. Otherwise it is
-           the Package ID of the root package.
+        /* The package in the current working directory (if \-\-manifest\-path is not given).
+           This is null if there is a virtual workspace. Otherwise it is
+           the Package ID of the package.
         */
         "root": "file:///path/to/my\-package#0.1.0",
     },