fix emojis

docs/lectures/cryptography/10_RSA.md

@@ -24,14 +24,14 @@
     - $gcd(a,m) = 1$
 - The **Euler totient** $\Phi$ is the number of integers in $\mathbb{Z}_m = \{0,1,...m-1\}$ for which $gcd(a,m)=1$
     - For example $\Phi(9)=6$ as:
-        - $gcd(1,9)=1$ :white_check_mark:
-        - $gcd(2,9)=1$ :white_check_mark:
+        - $gcd(1,9)=1$ ✅
+        - $gcd(2,9)=1$ ✅
         - $gcd(3,9)=3$ ❌
-        - $gcd(4,9)=1$ :white_check_mark:
-        - $gcd(5,9)=1$ :white_check_mark:
+        - $gcd(4,9)=1$ ✅
+        - $gcd(5,9)=1$ ✅
         - $gcd(6,9)=3$ ❌
-        - $gcd(7,9)=1$ :white_check_mark:
-        - $gcd(8,9)=1$ :white_check_mark:
+        - $gcd(7,9)=1$ ✅
+        - $gcd(8,9)=1$ ✅
 
 #### Integer Factorisation