How to remove all lines with text except lines with text;text?

Question

Regular Expressions

Hello. There is a text file.
The file contains the necessary lines text; text
After them there are unnecessary lines that need to be removed.
How to remove all extra lines except those in which the words are separated by a semicolon?
Here is an example file:
text;text
Unnecessary text, numbers
Unnecessary text, numbers
Unnecessary text, numbers
text;text
Unnecessary text, numbers
Unnecessary
text, numbers
Text;text
Unnecessary text, numbers
Unnecessary text, numbers
Unnecessary text, numbers