Use the TRIM function: `=TRIM(A1)`
Copy the formula down for the rest of the cells
Copy the results
Paste Special as Values to replace the original text
Use Find and Replace to remove extra spaces if needed
Select the range
Press Ctrl+H
Find what: two spaces
Replace with: one space
Click Replace All
Use CLEAN if non-printing characters are also present: `=CLEAN(A1)`
Combine CLEAN and TRIM: `=TRIM(CLEAN(A1))`
Use Flash Fill if the pattern is simple
Use Power Query to trim text in bulk
Use VBA if you need to remove trailing spaces from many cells automatically