chore: Match licensing with other plugins

plugins/single-instance/LICENSE.spdx

@@ -0,0 +1,20 @@
+SPDXVersion: SPDX-2.1
+DataLicense: CC0-1.0
+PackageName: tauri
+DataFormat: SPDXRef-1
+PackageSupplier: Organization: The Tauri Programme in the Commons Conservancy
+PackageHomePage: https://tauri.app
+PackageLicenseDeclared: Apache-2.0
+PackageLicenseDeclared: MIT
+PackageCopyrightText: 2019-2022, The Tauri Programme in the Commons Conservancy
+PackageSummary: <text>Tauri is a rust project that enables developers to make secure
+and small desktop applications using a web frontend.
+                </text>
+PackageComment: <text>The package includes the following libraries; see
+Relationship information.
+                </text>
+Created: 2019-05-20T09:00:00Z
+PackageDownloadLocation: git://github.com/tauri-apps/tauri
+PackageDownloadLocation: git+https://github.com/tauri-apps/tauri.git
+PackageDownloadLocation: git+ssh://github.com/tauri-apps/tauri.git
+Creator: Person: Daniel Thompson-Yvetot

plugins/single-instance/LICENSE_APACHE-2.0

@@ -174,4 +174,4 @@
       incurred by, or claims asserted against, such Contributor by reason
       of your accepting any such warranty or additional liability.
 
-   END OF TERMS AND CONDITIONS
+   END OF TERMS AND CONDITIONS

plugins/single-instance/LICENSE_MIT

@@ -1,6 +1,6 @@
 MIT License
 
-Copyright (c) 2017 - Present Tauri Programme within The Commons Conservancy
+Copyright (c) 2017 - Present The Tauri Programme in the Commons Conservancy
 
 Permission is hereby granted, free of charge, to any person obtaining a copy
 of this software and associated documentation files (the "Software"), to deal
@@ -18,4 +18,4 @@ FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
 AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
 LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
 OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
-SOFTWARE.
+SOFTWARE.