Updating issue templates again for rustbot

Author: xFrednet

.github/ISSUE_TEMPLATE/blank_issue.md

@@ -5,9 +5,10 @@ about: Create a blank issue.
 
 
 <!--
-Additional labels can be added to this issue by including the following command:
+Additional labels can be added to this issue by including the following command
+(without the space after the @ symbol):
 
-@rustbot label +<label>
+`@rustbot label +<label>`
 
 Common labels for this issue type are:
 * C-an-interesting-project

.github/ISSUE_TEMPLATE/bug_report.md

@@ -33,9 +33,10 @@ LLVM version: 10.0
 ```
 
 <!--
-Additional labels can be added to this issue by including the following command:
+Additional labels can be added to this issue by including the following command
+(without the space after the @ symbol):
 
-@rustbot label +<label>
+`@rustbot label +<label>`
 
 Common labels for this issue type are:
 * `I-suggestion-causes-error`

.github/ISSUE_TEMPLATE/false_positive.md

@@ -34,9 +34,10 @@ LLVM version: 10.0
 ```
 
 <!--
-Additional labels can be added to this issue by including the following command:
+Additional labels can be added to this issue by including the following command
+(without the space after the @ symbol):
 
-@rustbot label +<label>
+`@rustbot label +<label>`
 
 Common labels for this issue type are:
 * I-suggestion-causes-error