Fix syntax errors, update to Pester v5 syntax

tests/build/unit/unit.build.tests.ps1

@@ -4,18 +4,18 @@ Describe "$($env:repoName)-Manifest" {
 
     Context Manifest-Validation {
         It "[Import-PowerShellDataFile] - $($env:repoName).psd1 is a valid PowerShell Data File" {
-            $DataFile | Should Not BeNullOrEmpty
+            $DataFile | Should -Not BeNullOrEmpty
         }
 
         It "[Test-ModuleManifest] - $($env:repoName).psd1 should not be empty" {
-            $TestModule | Should Not BeNullOrEmpty
+            $TestModule | Should -Not BeNullOrEmpty
         }
 
         Import-Module .\$($env:repoName).psd1 -Force -WarningAction SilentlyContinue -ErrorAction SilentlyContinue
         $command = Get-Command $($env:repoName) -ErrorAction SilentlyContinue
 
         It "Should have the $($env:repoName) function available" {
-            $command | Should not BeNullOrEmpty
+            $command | Should -Not BeNullOrEmpty
         }
     }
 
@@ -24,11 +24,11 @@ Describe "$($env:repoName)-Manifest" {
             $module = Find-Module -Name $_ -ErrorAction SilentlyContinue
 
             It "Should contain the $_ Module" {
-                $_ -in ($TestModule).RequiredModules.Name | Should be $true
+                $_ -in ($TestModule).RequiredModules.Name | Should -Be $true
             }
 
             It "The $_ module should be available in the PowerShell gallery" {
-                $module | Should not BeNullOrEmpty
+                $module | Should -Not BeNullOrEmpty
             }
         }
     }