Update docs on new source-mapping-file argument (#1632)

* Update docs on new source-mapping-file argument

* Update GlobalTool.md

Author: jborean93

Documentation/GlobalTool.md

@@ -37,7 +37,7 @@ Options:
   --use-source-link                     Specifies whether to use SourceLink URIs in place of file system paths.
   --does-not-return-attribute           Attributes that mark methods that do not return.
   --exclude-assemblies-without-sources  Specifies behaviour of heuristic to ignore assemblies with missing source documents.
-  --use-mapping-file                    Specifies the path to a SourceRootsMappings file.
+  --source-mapping-file                 Specifies the path to a SourceRootsMappings file.
   --version                             Show version information
   -?, -h, --help                        Show help and usage information
 ```