Partially revert "Generate Manual" target name (#527)

- The name of "GenerateManualPlugin" was changed to "Generate Manual" to
  improve the plugin's display name in Xcode. This however results in
  the `.pluginWorkDirectory` provided by SPM to include a space (' ') in
  the path. The space in the output path by itself is not a deal
  breaker, but unfortunately `man` (at least on macOS) does not properly
  handle path arguments with spaces. Example:

  ```shell
  ➜  swift package generate-manual
  ...
  Generating manual for roll...
  Generated manual in '.build/plugins/Generate Manual/outputs/roll'
  ...
  ➜  man '.build/plugins/Generate Manual/outputs/roll/roll.1'
  /usr/bin/man: line 413: cd: .build/plugins/Generate: No such file or \
    directory
  ```

  IMO, easily previewing the generating manual takes precedence over the
  UI in Xcode; as a result, this commit partially reverts the plugin's
  name to "GenerateManual" to hopefully provide a good middle ground of
  an output path without a space and a display name in Xcode that is a
  little easier on the eyes than "GenerateManualPlugin" was.

Author: rauhul

[email protected]

@@ -19,8 +19,8 @@ var package = Package(
             name: "ArgumentParser",
             targets: ["ArgumentParser"]),
         .plugin(
-            name: "GenerateManualPlugin",
-            targets: ["Generate Manual"]),
+            name: "GenerateManual",
+            targets: ["GenerateManual"]),
     ],
     dependencies: [],
     targets: [
@@ -40,13 +40,12 @@ var package = Package(
 
         // Plugins
         .plugin(
-            name: "Generate Manual",
+            name: "GenerateManual",
             capability: .command(
                 intent: .custom(
                     verb: "generate-manual",
                     description: "Generate a manual entry for a specified target.")),
-            dependencies: ["generate-manual"],
-            path: "Plugins/GenerateManualPlugin"),
+            dependencies: ["generate-manual"]),
 
         // Examples
         .executableTarget(