Fixes auto-succeeding pester tests in AboutComparison and AboutStrings (

#214)

* Fixed "adds strings together" 

It "adds strings together" was passing the pester test without user input. Replaced the contents of $String1 with '__' so the user can solve it.

* Fixed It's that are autopassing the pester tests

Auto-passing tests:
It 'is a simple test'
It 'returns $true if either input is $true'
It 'negates a boolean value'
In all three instances, __ evaluates to $true, which causes the tests to pass. 

I replaced __ with $__ in these instances to make sure the tests fail.

* Updated $__ to $____ 

Added two extra underscores to each $__ to make sure no one will confuse $__ for $_

* Update PSKoans/Koans/Foundations/AboutStrings.Koans.ps1

Longer blanks! Better blanks!

Co-Authored-By: Joel Sallow (/u/ta11ow) <32407840+vexx32@users.noreply.github.com>

PSKoans/Koans/Foundations/AboutComparison.Koans.ps1

@@ -22,7 +22,7 @@ Describe 'Comparison Operators' {
 
         It 'is a simple test' {
             $true -eq $false | Should -Be $false
-            __ | Should -Be (1 -eq 1)
+            $____ | Should -Be (1 -eq 1)
         }
 
         It 'will attempt to convert types' {
@@ -168,8 +168,8 @@ Describe 'Logical Operators' {
 
         It 'returns $true if either input is $true' {
             $true -or $false | Should -Be $true
-            __ | Should -Be ($false -or $true)
-            __ | Should -Be ($true -or $true)
+            $____ | Should -Be ($false -or $true)
+            $____ | Should -Be ($true -or $true)
         }
 
         It 'may coerce values to boolean' {
@@ -193,7 +193,7 @@ Describe 'Logical Operators' {
 
         It 'negates a boolean value' {
             -not $true | Should -Be $false
-            __ | Should -Be (-not $false)
+            $____ | Should -Be (-not $false)
         }
 
         It 'can be shortened to !' {

PSKoans/Koans/Foundations/AboutStrings.Koans.ps1

@@ -102,7 +102,7 @@ Describe 'Strings' {
 
         It 'adds strings together' {
             # Two become one.
-            $String1 = 'This string'
+            $String1 = '_____'
             $String2 = 'is cool.'
 
             $String1 + ' ' + $String2 | Should -Be 'This string is cool.'